224 build question

#1
Hello! I am build two 224 predators for mini bikes. I have build several 212 and have had many years of experience with the Briggs (in karting). So the 224 has been a little bit of a pain with all of the clearance grinding needed. The biggest issue was the cam with the billet rod. I thought i got it all good, checked everything while rotating by hand. Started it up and there was a for sure ticking going on. Pulled it back apart and the compression release arm was contacting the crank weight. I ground out the spot on the arm, and touched up the crank just to remove the mark. Seems much better now. Has anyone ran into this? the crank is very close to the whole compression release assembly. thanks!
 
#2
I have read about the issue but if you are running the stock cam I dont understand why its hitting. Are you running a aftermarket cam?
 

SAS289

Well-Known Member
#4
Did you notice all the crankshaft end play? I got a shim kit and took all the end play out of the crank using shims on the PTO side of the crank. The cam got shimmed towards the side cover. I don't recall all the details but I used a Honda side cover gasket as part of the end play I was looking for. And did it without the proper measuring tools.

Don't remember where I got the shim kit but it had 3 shims for the crankshaft and 3 for the cam. Maybe ebay?

Which rod did you use? It looks like (other guys) with the EC carbs rod you don't have to clearance as much. I used an ARC rod. Had to clearance the side of the intake lobe of the cam because it was kissing the rod. And it wasn't because of the shims I used.

I thought it was a fun build. All I did was go for higher than stock compression (9.7:1), a higher than stock lift cam (252), a bored stock carb, and Champion rockers. Nice power for the RPM range I run.
 
#5
Yes I did check end play and tried without the side cover gasket. Then it was too tight. The shims make sense. I found them on eBay and ordered. So I will give that a try.
I am using an ARC rod. I decided to go a little further with these. Milled and ported head. Should be 12.5:1. Flat top Piston, bonsai 265 cam, mikuni. It sounds mean when is started it (minus the ticking from the compression release arm). Thanks for the suggestion!
 
#6
How did you measure the cam clearance when adding shims to the cam? I have been looking all over and can't find anything about that. Thanks!
 
#8
got it. thank you! i was looking at the one i didnt start on yet, and had the same thought yesterday. Still cant really measure it, but just make sure it still has some movement.
 
#9
The only way to check cam clearance is when you are assembling the engine. You have to put it together with just crank and cam then use a flat bar or long screwdriver to move the cam back and forth. Need gasket as well and side Cover bolts snug. You have to check for movement, disassemble then add a shim then reassemble and check again, you get the drill.
 
#10
Well i added shims to both the cam and the crank. I added one .006 shim to the crank (side cover side), and one .002 shim to the cam (block side). This gave me some movement on the cam and .014 crank endplay. Unfortunately the crank weight it still making contact with the decompression weight on the cam. I have ground a bunch off of the cam weight but still hitting. It actually broke the sping on the decompression again. So now... either i grind off more of the cam weight, or i thought about taking a little off of the side cover end of the cam so i could add more shims to it. I am very surprised this has been such an issue. Any other thoughts would be great. Thanks!
 

SAS289

Well-Known Member
#11
A .002" shim? The cam end play should be enough to go much more than a couple thou. I'm not sure what your next step would be.
 
#12
Just an update in case anyone is also running into a similar issue. I talked to Dyno Cams and they said there is a specific core that needs to be used on the 224. It has a different compression release assembly on the cam that is thinner. The only way i could get the cams i have work was to take off the second metal layer on the compression release arm. This is the part that looks like the weight. Also you need to flip the spring the opposite way otherwise the coils will contact the crank and break the spring. The cams that Dyno has are not listed on the site yet, but you can call and request any of their cams with the 224 core.
 
#13
Just an update in case anyone is also running into a similar issue. I talked to Dyno Cams and they said there is a specific core that needs to be used on the 224. It has a different compression release assembly on the cam that is thinner. The only way i could get the cams i have work was to take off the second metal layer on the compression release arm. This is the part that looks like the weight. Also you need to flip the spring the opposite way otherwise the coils will contact the crank and break the spring. The cams that Dyno has are not listed on the site yet, but you can call and request any of their cams with the 224 core.
I used just a regular super x 265 cam made for a gx200 in my 224 and only had to clearance between the lobes I didnt touch the comp release and it runs just fine
 
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