Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines
The Regular Stuff: Chat, Buy, Sell, Off Topic, etc. => General Discussion - Scale Model Gas Engines - Hit & Miss - Throttle Governed - Non-Compression – etc => Topic started by: engine-man on March 23, 2023, 03:05:44 am
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Thought to add more to the list
POWER SWITCH
I noticed the batteries on my R31 were getting hot and just die in no time, after some investigation I noticed the wires to the on and of switch weren't soldered well. I could only see that when I used magnifying glass . I disconnected them, cut the wires to expose new part and properly soldered them.
FUEL LINE:
First thing I ditch when I buy a Microcosm engine is the cheap fuel line, do yourself a favor and do the same, especially if you use anything like a lighter fluid, that reacts with the silicone in the line and causes uneven expansion. You don't need to add more to the issues here ...
Additional note on the fuel:
I tested the engine with VP Racing 40:1 fuel I have and it seems R31 likes it nore, is able to Rev more steadily and predictably. It works on coleman fuel as well but it was my observation.
Hope above helps to sort your R31 if having similar issues mentioned in this post. Happy to help if I can :)
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Got the engine running... spent an entire day and determined I won't quit until its sorted or I'm dead !
While I enjoy the look of R31 it has some design flaws which all contribute towards the issues I personally experienced. Here is a list and what I did to sort them.
CARB:
In my case I koticed the throttle, LSN and HSN screws are extremely sensitive.im talking about them getting out of tune even after 30 seconds of engine running or moving the throttle. First I thought I'm dealing with clogged and damaged carb, afger cleaning twice and measuring the position of each screw. I noticed any change even at 2/350 degree can knock the whole thing out of tune. Once I found the sweet spot, I used a small amount of super glue to hold them in place. Thats not the only issue however, the carb connection to the intake manifold is wobbly and wiggles up and down easily. Thay slight movement can easily introduce leak into the system.i tried to push them intake further in to secure it, however vibration of the engine after few mins of running makes it loose a again. The intake has two o rings which help with insulation but still not the best.
IGNITJON SYSYEM AND SPARK PLUGS:
I dislike these tiny plugs, they simply hard to find and pricey compared to the more common 1/4-32. The ignition leads usually are junk, you see lot of arcing marks on the shell of the plugs. To reduce the arcing, I connected a wire from the ground terminal and attached to under one of the foam legs. Not that it sort the flaw but reduces the arcing.
Now the ignition timing, Jin usually uses the wasted spark model in other engines he has or I came across. This is different in R31, it is a sequential ignition. While it's a great model the execution is not as accurate . I noticed to create a spark you actually need to rotate the flywheel at certain speed otherwise it misses to spark during combustion phase. Maybe it's just mine but somehow I doubt it. Why does it matter ? It does when it comes to trying to get a realistic Shovelhead low idle from this engine .
CAMSHAFT
biggest pain in the back side for this engine starts with the camshaft. Brass made unequal lobes ( in my case) and the way it us positioned and connected to crack shaft seems not very practical in a Vtwin setup. Few of us experienced premature wear on lobes ( on mine was middle two) after a very short run, resulting in engine not working. I ordered an upgraded one from Ebay and same thing happened to it in no time . Jin mentioned they are designing a new one and different material. While this part is an integral part of the engine, I found fiddling with cam lifter screws( at the bottom of pushrod tube can be a workaround, how long will it last ? I have no clue.
CAM/VALVE LIFTERS AND ADJUSTERS
The lifters connecting to the camshaft lobes on my engine didn't move up and down freely, I suspect this is one of the reasons the camshaft lobes were worn out. I sanded them with 1000 grit paper and added assembly lube , all 4 needed this. So check yours if you can
I am not the fan of how on R32 valves are adjusted . You have no actual way of seeing them work and have to take apart the valve cover and pushrod tubes, adjust the screws ever so slightly , put things back and try again. Really a big pain .
To check if yours are set correctly, test each cylinder. On intake there should be a good suction and equal for both cylinders via the carb inlet. And on exhaust stage you should have a strong push of air. If you notice any suction from the exhaust during the intake stage you need to adjust the valve.
What I noticed on mine were bent adjuster screws after putting inbthe new camshaft, I was lucky they didn't snap, I gently straighten them and closed both equally and run the engine to ensure it works okay and no more bending. Some assembly or design issues perhaps
FUEL
I am big fan of Coleman fuel mixed with Lucas uppercylinder lubricant ( similar to Marvel mystery oil ), however R31 gets really hot and the heat transfers to the carb very fast. Having a warm air and coleman fuel is not a good mixture and you will have issues with engine running. Unless you use a cooling method. I have a small desktop fan which I run close to the engine ( from behind) to push cool air.
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I totally agree, I can understand they need to go cheap so the price is reasonable ( ebay prices ) but in some areas they should pay more attention. I got full refund for this engine as I wasn't going to put up with it any longer.
I'm happy to be flexible and accommodating and even paid to get the new cam but I reached my limit and weren't willing to invest anymore time.
On the contrary to R31 my H75 works flawlessly and it's an impressive engine. I'm not expecting to last long but it works for time being at least.
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Stainless steel has extreme galling properties hopefully they can get it right otherwise stainless steel is gonna be a complete failure.
There’s no reason to reinvent the wheel here.
They need to use a Heat treat compatible on the cam and lifter. Cheapness is the cause of all these issues with these engines. No piston pin protection from galling into the cylinders is proof!
Piston pin retainers or Teflon disc like I have been suggesting is a very effective protection!!!
To the best of my knowledge None of these engines come with any form of protection between the piston pin and the cylinder walls.
It’s like having a built in ticking time bomb that will eventually ruin the engine the more you run it.
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Stainless steel has extreme galling properties hopefully they can get it right otherwise stainless steel is gonna be a complete failure.
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Another 4 hours piddling w’ my R31 went by yesterday, with still no luck getting it to run on both cylinders. I’m seriously at the point of buying another R31, and hoping this one runs and a stainless cam will be available.
Never have been stumped with an IC engine like the R31.. I’m 41 and have been taking apart engines since I was 6 years old. People in the neighborhood would give me their old lawn engines when they’d buy a new mower. Best “toys” I had as a kid
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There’s a lot of these engines being sold on EBay. I asked for a refund for the defective cam but he mentioned nothing of that. So I don’t think that will happen. 😟
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We need to make list of us and he has to send new cam shaft free of charge. Buy at least he's learning
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Hey guys, I got a message from Jin and he said they are working on a stainless steel cam for the Shovelhead. So maybe there’s hope! No ETA just said it takes time.
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Funny you mentioned hall sensor. Now i have very intermittent ignition. It quits after 4-5 ignition cycle. I noticed the engines gets quite hot even when it ran on one cylinder. And I turned on Mt desk fan to cool it down. The heart transfers quickly to the components under the base too.
I was thinking shovelhead would have any potential issues of knuckle head ironed out but it seems just a rushed product.
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I found also if I don’t keep a fan keeping the side of the engine that has the hall sensor it will start missing and quit. I have more of Jin’s engines so I switched ignition modules and hall sensors and the same results. I don’t have that problem with my Knucklehead. Seems this engine heats the sensor more. With the fan blowing on that side it keeps running. Another flaw.
I hope Jim can help. Keep me posted.
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I personally think the whole cam design is flawed specially for a vtwin engine
Not sure how much this particular ignition timing is affecting the overall performance as well.
I messaged Jin to see how he can help .
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Hi there, I’ve marked TDC and BDC for each cylinder on the flywheel. Checking the exhaust valve there is at least 20% difference when the exhaust valve starts to open as if the cam is ground in correctly. After trying the cam in different positions I finally got mine to idle decent. It still seems to favor the rear cylinder but the front cylinder will start to fire after warming up a bit. Kinda disappointed too. Nice looking engine but finicky.
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Hey guys,
I’ve lost another 10 hours of my life trying to get my R31 to run correctly. 😩
Ive never have had a miniature engine that I couldn’t get running correctly, with some work and time, but my god - I’m about to give up. Don’t wanna know how many hours I’ve put into mine, and simply can’t get my R31 running on both cylinders. The tank side cylinder runs strong, but the opposite cylinder refuses to run. Strong spark at the right time, correct valve clearance, compression, I just can’t figure it out.
Gonna tear the engine down completely and see what I can find out. So far, the new cam hasn’t worn.. but will be watching it closely.
I absolutely love my R29 Knucklehead. It’s got easily over 40 hours on it, and it’s a “one flip wonder”
I had such high hopes and excitement for Jin’s R31 Shovel. I chose it over Jin’s Panhead.
Just bummed 😔
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Hi, yea I can’t figure it out other than the brass was to soft. The old cam is worn a little but not too bad. I purchased the new cam because the new I read was supposed to give you a better idle.
The pushrod tubes have a threaded bottom section that I guess is supposed to screw up far enough to adjust the valves. Won’t screw up far enough on mine. So I pull the rocker box and put one pushrod in at a time, put the cover back on with a couple of screws and adjust the tiny screw on the lifter. They are loctited so you may have to heat them a bit. I’m sure they would twist off easily. A pain but that’s how I do it. I hope this helps. My lifters seem to be not sticking. The old cam still works and not getting the lobes destroyed so idk.
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That's really bad the new cam worn off. Brass is not the right material for gears. I would have asked for a refund to be honest.
One thing I noticed on mine was the vavle covers in the crankcase were not moving up and down easily . I have to sand them off to have a free movement. I think that might have caused the wear on yours and mine.
New cam shaft seems to holding okay. How do you set the valve setting? Through the screw on the lifter at the bottom?
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Hi Engine-Man,
I have the IR31 Shovelhead. I bought the new cam thinking it would idle better. The first tank of fuel it ran great. After the third tank it quit running. I discovered the lobes were wiped on the new cam. Too soft maybe? So after cleaning out all of the debris in the cavity I put the original cam back in and with much frustration and work it seems to be running on both cylinders for now. I’ve found the valve clearance is pretty critical. About a 1/2 mm seems about right. And the carb is extremely touchy also. So disappointed about the new cam.
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An update on the R32, couldn't be ignorant towards the engine and the itch to make it work again didn't stop. So I ordered the new camshaft which basically has more pronounced middle lobes.
Despite that still struggling to make this run on both cylinders.
I am aware of another case of the struggle but is there anyone else who bought this engine and having issues getting a stable and reliable run out of it ?
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I put my engine aside and thought to focus on something else.
Mine doesn't start and it is the faulty camshaft. Needs the upgraded one($20) but can't be bothered to wait for Jin. If someone wants it I'm happy to sell it for $300USD plus international shipping through PayPal. Could do with a better home :) feel free to PM me
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My thoughts exactly. I’ve ordered a piece of Teflon Ptfe from eBay.
I had low compression on the front cylinder of the Knucklehead.The piston o-ring apparently was pinched during assembly. When replacing the ring I noticed the scoring in the cylinder wall. Enough you can feel it with your nail. So I took the old ring and cut it in smaller pieces and fit it into the piston pin opening on each side. I’m pretty finicky about things.
When I get the Teflon I will cut the discs and put them in the R31.
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I sent a message to Jin asking him to reply and he did. I told him I heard you had an updated camshaft for the R31. So waiting on a response.
You’re the man! You’ve given me nothing but good advice! The engines love the new fuel mix.
Have you noticed the floating wrist pins have no retainer so the pin comes out and scores the cylinder wall? Just wondering what your fix is for this bugga boo.
That’s awesome man! Yep, I’ve noticed the floating wrist pins, but haven’t yet done anything just yet… glad you reminded me.
My plan is to get an extremely thin sheet of Teflon or ptfe, and use a small leather punch to punch out some tiny discs I can use on each side of the piston pin. I know someone on the forum has done something similar on their H74 or H75.
I’d planned on doing this for my Knucklehead once it needed the o rings replaced, but since using MMO the o rings definitely don’t need to be replaced… if anything the compression is much stronger than when it was new. And I’ve put a lot of hours on my little knucklehead
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I sent a message to Jin asking him to reply and he did. I told him I heard you had an updated camshaft for the R31. So waiting on a response.
You’re the man! You’ve given me nothing but good advice! The engines love the new fuel mix.
Have you noticed the floating wrist pins have no retainer so the pin comes out and scores the cylinder wall? Just wondering what your fix is for this bugga boo.
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Hi, I just tried the Coleman fuel and Marvel Mystery oil mix and works great. Thanks for another good piece of advice. Doesn’t stink the house up as bad 😂
Haaa you’re welcome dude, yeah… once you go to Coleman fuel and MMO, you’ll never go back. Clean burning, virtually no carbon deposits or smoke.. I love it. The MMO is also great on the O-rings… it prevents swelling unlike some 2 stroke oils.
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Hi, I just tried the Coleman fuel and Marvel Mystery oil mix and works great. Thanks for another good piece of advice. Doesn’t stink the house up as bad 😂
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Lol… I run mine in the house too. Have to open the door and air it out sometimes 😊
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That’s awesome man! Glad to hear you got your R31 running 🤙
Definitely try Coleman camping fuel & marvel mystery oil; it works great… and my gf doesn’t mind too much when I start my engines in the house 😂
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Thanks for the advice. I own an R29 Knucklehead as well. I call it my star pupil as it starts easily and runs well…lol.
I got the Shovelhead running with your help. I’m going to convert to the fuel mix that you’re using. I’ve tried Zippo mix, different gasoline mix’s. The engines Seem to idle nicely but don’t rev the way they should. I’ve tried adjusting the carburetor but doesn’t seem to help.
Again thanks for your advice!
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Hi Gamma13r,OMG! Thank you so much for the diagram!! Let me know how the new cam works out. The cam lobes in my engine are sad looking. I’ve tried to contact Jin through eBay twice and haven’t got an answer. Any secret to getting him to respond? Again thank you for the diagram!
Of course & no problem!
Sometimes getting a hold of Jin can be tricky, but I know it’s bc he’s so busy… Here’s what I have done - if he doesn’t get a hold of you in a few days after you sent your message on eBay, sent him another message on eBay and just ask if he could contact you back. -here’s what I think also happens: eBay has a bot that scans messages for people looking to buy goods from sellers outside of eBay; and they delete messages that even remotely sound like any purchase. sometimes I think that my messages haven’t gotten to Jim, bc eBay has deleted them.
Jin is a really good dude and he will get back to you, just takes a bit sometimes.
How he develops so many different miniature engines is beyond me.
As soon as my camshaft arrives, I will report back and let you all know the changes. I’m sure it will help a lot. I own an R29 Knucklehead, and it loves to run…and run extremely well.
I have probably put at least 35 hours on it, since I got it last November. It’s always a “one flip wonder” - idles and revs beautifully, no oil splooge & no smoke. I have a lot of confidence in the R31 shovelhead, it just needs some tweaks and tuning.
I run all of my miniature engines on Coleman camping fuel and marvel mystery oil @ around 45:1, and I run my engines a lot… all of my engines seem to love it.
I’m “ 133mhz “ on YouTube 🤙
Hope this helps dude - as soon as I get my Camshaft I’ll report back
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Hi Gamma13r,OMG! Thank you so much for the diagram!! Let me know how the new cam works out. The cam lobes in my engine are sad looking. I’ve tried to contact Jin through eBay twice and haven’t got an answer. Any secret to getting him to respond? Again thank you for the diagram!
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vbiker,
I forgot to mention the updated camshaft;
I ordered mine from Jin directly, it costs $22 including shipping. Jim said the updated cam is supposed have a lower idle and better running characteristics.
Looking forward to when mine arrives
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Hi guys, I’m new here and I have the shovel head engine. And as you say when you take the cam cover off the cam comes out with it . No timing marks. I’ve been trying to get a hold of Jim for a while and no reply. You say he has an updated cam and you have the valve timing diagram? Wow! Could you help me please? It would be greatly appreciated! Thanks 😊
Hey vbiker 👋
It happens dude.. After having issues w’ my R31, I got ahold of Jin and asked him about the cam / flywheel timing. Here is a diagram Jin sent me that will help
Position the grub screw on the flywheel straight down, then install the camshaft with the 2nd cam lobe pointing straight down
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Hi guys, I’m new here and I have the shovel head engine. And as you say when you take the cam cover off the cam comes out with it . No timing marks. I’ve been trying to get a hold of Jim for a while and no reply. You say he has an updated cam and you have the valve timing diagram? Wow! Could you help me please? It would be greatly appreciated! Thanks 😊
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It's will be interesting to see if the new camshaft will sort the problem. The left cylinder ( opposite fuel tank ) simply doesn't want to work. I noticed it is sucking air through the exhaust pipe. Properly an issue with valves and the timing of the camshaft.
It's hard to properly diagnose it without seeing the valve rockers in action unlike other harley engines made. I made it to the point that engine was properly sucking fuel from the carb and managed to run couple of times for 10-15 seconds then died.
If someone else has this engine, it would be good to share your experience and perhaps issues
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Hey engine-man, I just sent you a message on Facebook messenger, Mr. Jin got back to me. I sent you a picture of the diagram he sent me.
Once you get your shovel timed, I need your help in the correct magnetic gear position in relation to the crank being at bottom dead center.
Talk soon man, Jon Cook
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engine-man,
I contacted Jin on EBay, and asked him about the cam. He said it costs $22 with included shipping. He sent me his PP info and I bought one, and also sent him some extra $ bc he said he will draw me out a cam / flywheel / magnetic trigger timing diagram for the shovel. Hope he’s able to draw it for me soon… know he’s really busy. Soon as he sends me the diagram I’ll send it to you on FB messenger 🤙
Sounds awesome ! I hope he replies to me too.
Sharing the diagram would be really appreciated ;D
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engine-man,
I contacted Jin on EBay, and asked him about the cam. He said it costs $22 with included shipping. He sent me his PP info and I bought one, and also sent him some extra $ bc he said he will draw me out a cam / flywheel / magnetic trigger timing diagram for the shovel. Hope he’s able to draw it for me soon… know he’s really busy. Soon as he sends me the diagram I’ll send it to you on FB messenger 🤙
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Hey engine-man & Gil,
Wanted to give you an update, I have talked to Mr. Jin, and actually ordered one of the updated camshafts.
I also asked him if he will please draw me a diagram of the R31’s ignition timing and cam timing, I’m just waiting on when he will be able to draw it for me… I’ve been so excited to hear my shovelhead run; when I received mine from eBay, it had a lifter completely stuck, so haven’t been able to hear it yet.
That's awesome to hear. How did you order the updated camshaft ?
They said they were sending me one but then went radio silent.so not sure if it was sent or not.
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Hey engine-man & Gil,
Wanted to give you an update, I have talked to Mr. Jin, and actually ordered one of the updated camshafts.
I also asked him if he will please draw me a diagram of the R31’s ignition timing and cam timing, I’m just waiting on when he will be able to draw it for me… I’ve been so excited to hear my shovelhead run; when I received mine from eBay, it had a lifter completely stuck, so haven’t been able to hear it yet.
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This is a great thread, guys!
You have posted valuable info here.
Gil
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Does anyone else with this engine has issues with camshaft? I took the cam cover to inspect the parts and camshaft came out with the cover. There are no timing marks onneither cam or crank gears. Tried many standard combinations but engine fails to suck fuel.
I know microcosm made a revised camshaft but I can't find it on ebay or their website yet
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That's an awesome find Gamma !
I'm planning to return this engine to them, so prefer not to thinker with it. Although it's good to see there is a way.
I was thinking to make shorter push rods, that way the vavle will be properly closed. And extend the exhaust one to allow better scavenging to achieve true Harley low RPM character. I did that on my R90S and it idles low and beautifully after it's warmed up.
I must say this engine has lots of potential but needs a bit more comprehensive design. Specially with the V35 angle there will be lots of shaking and vavle adjustment ability ( probably in easier way) is needed. The crankshaft also seems a bit thin. Whilst by design there is no load on the engine, overtime I wonder if it will lose its shape and strength, especially as the large camshaft gear and the ignition timing gear feed of it.
Sad to return it because my friend would have loved it but don't want to disappoint him with constant tinkering needed.
I am waiting to get H75 engine. Apparently it comes with the upgraded cylinder to prevent coolant leak. Fingers crossed it will have minimal issues !
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Hey engine-man,
upon closer inspection, there is a way to adjust the valves, I just adjusted mine, and no longer have compression leaking out of the carburetor.
-notice the lifters have a small hex bolt threaded in to the lifter itself.
I removed the lifter block, and gently heated (with a heat gun) the lifter that was causing the leaking intake valve.
This has to be done with a lot of care not to scratch the lifter or break off the hex bolt’s tiny threads. The hex bolt is held in place with loctite; so I gently heated the threads of the bolt, and used a tiny pair of needle nose pliers to run the hex bolt 1/2 turn in clockwise, exposing less threads and giving more clearance to the valve lash.
I’m going to work on cam timing when I get back home today…. After studying Mr. Jin’s videos, his R31 is definitely running & turning clockwise just like his other V twins. I absolutely love my knucklehead engine, after getting it broken in, it runs beautifully. And, like you mentioned in another post, the only thing I would like to see different on these engines is the exhaust pipe design… I wish in the future that Mr Jin will make a set of chrome / stainless slash cut pipes as an option
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Another thing i do is to wrap a thin exposed wire ( without the shield ) around spark tip. This will provide a direct contact with the ignition leads. That will reduce the arcing else where too
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Aren't these engines full of surprises? Haha
I was also surprised knowing there is no way to fine tune the valves, mine has a faulty cam shaft which is the source of many issues I assume. I was thinking my R90s was difficult engine but at least with that one there is some room for adjustment.
Jin has upgraded cam shaft which I believe he would send to the customers. That will hopefully sort array of problems.
When I opened the crankcase to inspect the camshaft it came out with the case cover. And there are no cam timing marks to readjust it.
Hopefully Jin will provide a guideline.
I am not big fan of these tiny sparks, they are fragile and I think their life span is shorter than likes of 1/4-32. And can only find them through their ebay/starlingkits. With 1/32-4 spark type, RCEXL makes great quality both in standard and Iridium variant. They work great on R90s.
I got this engine to give as a gift to someone, but I think I will return it as the receipt is not that mechanically minded. I was expected the newer engines are defect free.
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Engine man…
I thought I was the only one who had a shovelhead that runs counterclockwise!! I did the exact same thing you did, and went to watch Mr Jin’s videos, and I also noticed that he starts his engine, and it runs clockwise just like his other V twins…
When I received my shovelhead, it wouldn’t run at all, it turns out it had a lifter stuck… I removed the valvetrain and easily freed the lifter, & reassembled it. I have been trying to figure out the valve timing because mine also fires out the carburetor.
I have been trying to contact Mr. Jin for a cam, timing, diagram, but have not heard back from him. I came here thinking I might be able to find his direct email
We will get it figured out… glad to know I’m not the only one, but also sucks that you’re having problems also. I do have a Knucklehead cam timing diagram, but it’s different than the Shovel’s cam timing
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Mike,
I’ve found an easy way to prevent my Knuckle from jumping spark… use a dummy battery to reduce the CDI power from 4.5 to 3 volts. You can get a dummy battery on Amazon. After I did this with my knucklehead, I haven’t had an issue since.
Since this didn’t solve your problem, have you tried adding a piece of silicone tube to the body of your spark plug?
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I’m going to try your grounding method.
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Maybe the issue is the grounding. I extended the ground connection to one of the foam legs with a piece of wire.
Bit expensive models to just look at haha
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I have one of these Shovels and I also have the knuckle. The knuckle runs ok, but I have a problem with inconsistent ignition and the spark shorts over the outside of the spark plug insulator. I cut the voltage back by eliminating one battery and that seemed to help some. I haven’t tried to start the shovel and may not ever. I just like looking at them. I have a real Shovelhead to run if I want and it sounds much better! Lol
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Hi all,
Just thought to post about me recently purchased Microcosm R31 ShovelHead.
It's a beautiful engine to begin with. Delicate, detailed ( for what it is ) and presented nicely.
I was surprised to see it is smaller than my R90s with tiny spark plugs ( 3/16-40) which I couldn't find the main manufacturers made one ( RCEXL ).
Interesting fact was when I was watching the videos of it on YouTube. It shows it starts clockwise but the one I got turns anti clock wise. Not an issue for me.
One thing I have problem with is the left cylinder doesn't fire right and exhaust gas is minimal. And other exhaust is quite loud. There is a fuel leak from the carb intake too.
I messaged Jin to see how can I adjust the valves on this model so it should be good I hope.
Does anyone else have this engine or other shovelhead model?