Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

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?

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

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?

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.

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

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

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.

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 🤙