The kid got an engine to run last night, he found a new red box stock clone, On the hot laps it ran great for half a lap then started popping and running bad at higher RPMs. Brought it to our pit, when he revved the engine it ran rough popping and spit fire out the exhaust. I checked valve clearance, it was good. He was using a carb from his other engine, so to rule that out we changed the carb back to what cake with his engine. Still not right. I checked his coil gap, it was set at .030. I reset it to .035 and it ran a little better for the heat race but after 5 or 6 laps started popping and sputtering at wide open. Another guy at the track put his degree wheel on it and said the timing was off. He said timing was at 22 degrees. He reset timing with his degree wheel, but must have been off because it would not start. I pulled the flywheel again (ARC billet flywheel) and saw the key slot in the flywheel was gouged out. I was in the process of trying to get the flywheel on with a stock key when we were called to staging so he didn’t make the feature race. He is bringing the engine to my shop today, I am going to try to get it figured out. My only thoughts are flywheel or the coil is bad. We also changed valve springs hoping that would fix the problem. I pulled the side cover and his timing marks are lined up properly. Do any ideas of what else to check out to solve the sputtering and cackling at wide open?
Requesting assistance with clone.
- Thread starter jacobsdad
- Start date
Chris Cooper
Member
Cam timing ok ?
I decided to pull the head instead of a leak down test, the intake valve was not seating. Brand new junk. Also the rod was too tight, when we finally got it running good it got too tight and died. So we put the rod and crank you gave him in it, I think we have it. Running good on the bench! We are taking him to a race out of town with us, so we will see how it goes. He is very thankful for the help and the parts!
Going to post a better list of the kids problems. He decided to get a red Clone motor to finish the season. Last night at the track he made it one lap in the hot laps, engine ran great with plenty of speed. Second lap it started popping and sputtering at wide open and spitting fire out the exhaust when he accelerated. He brought it to my trailer, I checked valve lash and checked coil gap. He was running it at .030, and it looked like one side had slipped as it was a smaller gap. I reset him to .035. He had put a different carb on it with a 37 jet. He changed to a different jet, I forgot already which jet. Went out for the heat race it ran great for a lap or two then started again. As the race went on it got worse. Brought it back in, we changed the plug changed to a different carb and checked his timing. Another guy at the track checked with a degree wheel and thought his timing was behind. He reset it and it would not start. I was in the process of changing his timing but ran out of time so he missed the feature race.
today he brought the engine to my shop. I changed from the ARC flywheel to a PVL that I had. The ARC flywheel had a key shear last year and the key slot was chewed up. Started it and still had the problem at wide open. Changed the coil to one I know is good, put my timing light on it to double check timing, still wouldn’t run right, changed carbs again with oneof mine, no change. Changed spark plug again, no change. I checked the length of his push rods and found there was a big difference in lengths between the intake and exhaust. I didn’t figure that would cause the problem but changed them out with a set I had. We also changed to a new set of valve springs. Still no change. But this time while letting it sit and idle the engine sounded like it was bogging down, then it died suddenly.When it died it stopped instantly like it was locking up. Pulled the rope and it was very tight. We pulled it apart and Changed out the crank shaft and connecting rod with one he got from a member here. When he had the head off I looked and the valves did not look right. They were not closing right. I had an engine here that my daughter blew up a couple of weeks ago with a decent head so I changed heads. Finally it runs good! the brand new clone had a faulty head and the rod was too tight, I put the rod that came with the engine on 2 different crank shafts and it was way too tight. I couldn’t hold the crank and twirl the rod, it was tight enough it wouldn’t spin free.
Tomorrow we are taking him with us to a race out of town, hopefully it finally runs good for him. I also switched the cam with one I had just in case it was messed up too. He has a block at home, he wants me to help him build that one for a spare. Looks like I need to do some studying to learn how to check cam timing and a few other things. We let the engine sit and run at medium RPMs for 15 or 20 minutes, all looked and sounded good so we went fishing.
today he brought the engine to my shop. I changed from the ARC flywheel to a PVL that I had. The ARC flywheel had a key shear last year and the key slot was chewed up. Started it and still had the problem at wide open. Changed the coil to one I know is good, put my timing light on it to double check timing, still wouldn’t run right, changed carbs again with oneof mine, no change. Changed spark plug again, no change. I checked the length of his push rods and found there was a big difference in lengths between the intake and exhaust. I didn’t figure that would cause the problem but changed them out with a set I had. We also changed to a new set of valve springs. Still no change. But this time while letting it sit and idle the engine sounded like it was bogging down, then it died suddenly.When it died it stopped instantly like it was locking up. Pulled the rope and it was very tight. We pulled it apart and Changed out the crank shaft and connecting rod with one he got from a member here. When he had the head off I looked and the valves did not look right. They were not closing right. I had an engine here that my daughter blew up a couple of weeks ago with a decent head so I changed heads. Finally it runs good! the brand new clone had a faulty head and the rod was too tight, I put the rod that came with the engine on 2 different crank shafts and it was way too tight. I couldn’t hold the crank and twirl the rod, it was tight enough it wouldn’t spin free.
Tomorrow we are taking him with us to a race out of town, hopefully it finally runs good for him. I also switched the cam with one I had just in case it was messed up too. He has a block at home, he wants me to help him build that one for a spare. Looks like I need to do some studying to learn how to check cam timing and a few other things. We let the engine sit and run at medium RPMs for 15 or 20 minutes, all looked and sounded good so we went fishing.
No my daughter caught a small catfish, the other kids mom caught a small white bass and the kid caught a pair of swim goggles. But it was a good time.
Petty Race Engines
Member
Jody has some great tutorial videos on the ARC Facebook or you gam search them by ARC racing, highly recommended these videos for the beginner.. he does a fantastic job of explaining it
I have watched the videos on ARC before. A lot of great information.
an update on the kid and his engine troubles. So he had the brand new clone that make it a couple of laps then lost power and wouldn’t run. I found out the rod that came with the engine was too tight on the crank, even just snugged up a little not fully torqued it wouldn’t spin free on the crank. Replaced that with a crank and rod he got from a member on here. Found a valve was not seating so replaced his head with one I had. It looks to me like the valve guide isn’t straight. It ran great and idled good. We ran it about a half hour on the bench. Went to the track last Friday and it ran great to start the heat race, then lost power and tightened up again. it was hard to pull the rope and it struggled to run. He was only turning 6400 RPMs abs the temp was around 325 so I don’t think he cooked it. He is using the same oil he has always used, the same oil his dad had in his kart so I don’t think it is oil related. I think the bore in the block might be messed up, either it is too small and the piston is getting tight or it is not bored straight putting side torque on the rod. The only thing I didn’t measure when we built the engine was the ring gap, but we used the factory piston that came with the engine. So for the feature I gave him our spare engine. It isn’t much on power, we have ran it for a year and a half but it ran for most of the feature for him. The exhaust stud worked loose and started rattling. In the rush to get the engine on his kart I didn’t take time to wrap the safety wire through the studs. When he heard the rattle he was afraid to wreck our engine abs pulled in.
I told him to check the threads on the exhaust bolts, wire them together, change valve springs and finish the season with our engine. It won’t be fast but it is better than sitting on the sidelines watching. We will see how tonight goes for him.
an update on the kid and his engine troubles. So he had the brand new clone that make it a couple of laps then lost power and wouldn’t run. I found out the rod that came with the engine was too tight on the crank, even just snugged up a little not fully torqued it wouldn’t spin free on the crank. Replaced that with a crank and rod he got from a member on here. Found a valve was not seating so replaced his head with one I had. It looks to me like the valve guide isn’t straight. It ran great and idled good. We ran it about a half hour on the bench. Went to the track last Friday and it ran great to start the heat race, then lost power and tightened up again. it was hard to pull the rope and it struggled to run. He was only turning 6400 RPMs abs the temp was around 325 so I don’t think he cooked it. He is using the same oil he has always used, the same oil his dad had in his kart so I don’t think it is oil related. I think the bore in the block might be messed up, either it is too small and the piston is getting tight or it is not bored straight putting side torque on the rod. The only thing I didn’t measure when we built the engine was the ring gap, but we used the factory piston that came with the engine. So for the feature I gave him our spare engine. It isn’t much on power, we have ran it for a year and a half but it ran for most of the feature for him. The exhaust stud worked loose and started rattling. In the rush to get the engine on his kart I didn’t take time to wrap the safety wire through the studs. When he heard the rattle he was afraid to wreck our engine abs pulled in.
I told him to check the threads on the exhaust bolts, wire them together, change valve springs and finish the season with our engine. It won’t be fast but it is better than sitting on the sidelines watching. We will see how tonight goes for him.