I have a black mamba cam and newly installed in my honda 160 . When i got it i noticed that the release was different than the one on the stock honda cam , so i figured that it was a clone core that was used . But i seem to have a problem of it not completely turning itself off or slightly hanging up . When its hot and I tried to restart the motor finally started but barely ran like the release was not fully off , after a minute or so it kicked off and ran find . Anyone know how i can fix this problem ?
Compression release problem
- Thread starter David wulf
- Start date
- Tags compression problem release
Metal expands as it gets hotter,the lash for that cam is .005 and there is a reason for it. I have a flathead 5HP modified and the lash for the cam in it is .008, if it is not set to .008 it will loose comp once the engine reaches running temp. expansion contraction plays a roll in where you set the lash,you cannot out smart it.
I cant say on a flathead, I assumed when he said a Honda 160 he meant a gx160, OHV engine. I set lash at as close to zero, and when hot I have PLENTY lash. I have been building engines for 30 years. On a cast iron head (say a limited sportsman engine) there isnt a lot of change from cold to hot, but..on my 406ci, SB2.2 headed engine I set lash at .006 cold and have .018 hot.
Let me put it this way,if your spinning the engine @3600 rpm then you can set the lash tight.Once you start spinning that engine to twice that RPM you need more lash or you run into problems and it definitely has to do with expansion.I've been messing with motors a long time too and I never put my hands on one I couldn't make go faster, just sayin:shrug:
Not trying to argue either. I turn my kart engines 7300 to 7500 and set the lash as close to zero as possible cold. I will try to check one soon to see the change from cold to hot, but its a pretty good amount. I have had the cover off hot and felt of the lash, but not really checked it with feeler guages. I just have a backyard track, so my engines arent anything extreme. I have worked on several clone racing kart engines (BSP to S/A) and know for a fact that keeping the lash tight as possible will show more power. I have a friend with a good S/A engine, and I set the lash tight as possible cold. Its turned 8200 to 8500 every lap (at a real track) lol
I have a Black Mamba in one engine too. They run good dont they? I have some mod2 cams in other engines that do real well too (all on just gasoline). I think the mod2 may be a little better down in the lower rpms, but the Black mamba pulls great up high. I have turned it 7600rpm and it loved it. I have another cam coming from Tim (Isky) for a stock appearing that I am building that needs to turn 8200 to 8500. I hope I didnt come off as trying to be rude, or a know it all, just stating what I have learned.
David I am fighting the same issue. Have used a number of these cams with great success but on all I was using a electric starter. This latest project is on a mini-bike and after setting the engine up and getting jetting correct I stopped using a electric starter and installed the rope pull starter. It is very hard to start as with the enrichment lever on it sort of starts but fires quietly out of the exhaust and I have to play with the throttle to get it to run fast enough for the compression release to swing out at which time the exhaust gets real loud and now the engine idles fine. I noticed that there is very little compression when pull starting the engine so I did a leakdown test and found that i had a bit of a leak on the intake valve. Pulled head redid the seat and vacuum tested seal was better so when reinstalling the head I noticed that on the compression stroke when the intake is closed the compression release raises the exhaust pushrod for almost the complete compression stroke returning to the base circle of the cam about 3/8th of an inch before TDC. before removing the head I tried loosening the exhaust valve but it did not help. Tomorrow I will finish reassembling the engine and see if the starting situation is any better. I also set lash at .003 go .004 no go. I have lash caps on both valves and am afraid to get it too loose or they may fall out.
Ond 4 what you discribe sounds exactly what mine is doing . I think i'am going to pull my cam out and check the release . What i really want to do is send my cam back to Tim and also send my honda core, have him grind it and i will have a honda cam and release because there is a diff in a clone and honda release .
