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Pinch at top of stroke?
- Thread starter rfraser
- Start date
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There should still be some degree of resistance when trying to pop it over TDC. Nowhere near as much as with the plug in, but it still should pop.
If you're worried about pinch, take the cooling head off and cycle the engine by hand. The piston should still remain somewhere near 1/8" below the top of the sleeve. If it's even with the top or protrudes, you're pinch is shot and you should replace the piston/sleeve.
If you're worried about pinch, take the cooling head off and cycle the engine by hand. The piston should still remain somewhere near 1/8" below the top of the sleeve. If it's even with the top or protrudes, you're pinch is shot and you should replace the piston/sleeve.
Scrogg
Hardcore RCTalk User
When an engine is fully broken in it will pop at the top of the stroke but feel smooth with the glow plug out. If it still feels like metal to metal contact, the engine is not finished breaking in.
Not sure what you mean here Candyman, the pinch has nothing to do with how far up the piston travel is while assembled. IF the piston/sleeve is out then this would be correct info. If the piston comes that far up while assembled , you have a major problem like con-rod stretched or about to break.
- Thread starter
- #5
Went camping for the night. Just got your replies. Maybe i should start another thread but this is where it all started.
Had a gallon of 20/16 through the engine for break in and it always run extremely hot, it hit 280-290 buy the end of a tank but run pretty well and even doing some wheelies. Switched to 20/12 and started to retune it. When starting on first tank of new fuel I forgot to turn on the controller, it started to rev wide open, i was luckly to get my hands on it, i just held it hard against the ground to stop it and pinched the fuel line at the same time to kill the engine.
Put everthing away for the night and recharged all batteries. The next day, with the new fuel, it started fine and run for a bit(much cooler) but seemed to be running way rich, before I got a tank of fuel through it couldn't pull its own weight. Stumbling and farting and usually quit as soon as I touched the throttle(with new plug). Went back to factory settings and still the same. Adjusting needles seemed to do nothing. was wondering if I may have hurt the engine, top of piston looks ok and cylinder walls look ok through the exhaust port.
I know, maybe not enough details, just looking for some where to start. I can easily turn it over with my fingers with the plug out with a slight pinch at the top.
Appreciate any suggestions. Thanks Rob.
Had a gallon of 20/16 through the engine for break in and it always run extremely hot, it hit 280-290 buy the end of a tank but run pretty well and even doing some wheelies. Switched to 20/12 and started to retune it. When starting on first tank of new fuel I forgot to turn on the controller, it started to rev wide open, i was luckly to get my hands on it, i just held it hard against the ground to stop it and pinched the fuel line at the same time to kill the engine.
Put everthing away for the night and recharged all batteries. The next day, with the new fuel, it started fine and run for a bit(much cooler) but seemed to be running way rich, before I got a tank of fuel through it couldn't pull its own weight. Stumbling and farting and usually quit as soon as I touched the throttle(with new plug). Went back to factory settings and still the same. Adjusting needles seemed to do nothing. was wondering if I may have hurt the engine, top of piston looks ok and cylinder walls look ok through the exhaust port.
I know, maybe not enough details, just looking for some where to start. I can easily turn it over with my fingers with the plug out with a slight pinch at the top.
Appreciate any suggestions. Thanks Rob.
Scrogg
Hardcore RCTalk User
I doubt you fried it that easily but it can happen. You just slightly accelerated the engine wear at the most. Lean it down further on both needles, it just sounds like it is overly rich.
RC Addict
RCTalk VIP
+1 It sounds slobbery rich right now.
- Thread starter
- #8
Rich is the first thing I thought as well but I thought going from 20/16 to 20/12 fuel that it would have been running leaner if anything as wear it was running farely well on 20/16 or am I not under standing this fuel thing.
I took the motor completly apart and there doen't seem to be any abnormal wear, piston,sleeve and head look good. No burns,scuffs or pitting any where.
Would going to the 20/12 fuel creat that much trouble?
I took the motor completly apart and there doen't seem to be any abnormal wear, piston,sleeve and head look good. No burns,scuffs or pitting any where.
Would going to the 20/12 fuel creat that much trouble?
RC Addict
RCTalk VIP
Less oil content will not necessarily equate to a leaner condition. You are still running 20% nitro. And no, I can not see where going with 4% less oil would have that huge an effect. I run 20/12 in all my rigs and can honestly say they run better now than they did with higher oil content fuels.
- Thread starter
- #10
It seems like I'm making some headway BUT does it seem right to be in 3 full turns from factory on HSN before I can get it to run half right at all. I actually had to turn the HSN on the stand to get it to run there was that much oil coming out of the exhaust(likely not a good thing to do). I think I still have to go more on the HSN to get it tuned right.
Scrogg
Hardcore RCTalk User
3 turns in on the HSN is normal for that brand of engine. The factory HSN is WAY too rich. Axial makes that engine as well as the K4.6. They use pretty much the same carb on all of them. Don't forget about the LSN, I'm sure it needs some tweeking as well now.
- Thread starter
- #12
Thanks for your help, enough help to atleast make everything seem normal. Got it to wear it will run half decent in the stand, which it wouldn't do before. See what happens when I put the rubber to the ground.
- Thread starter
- #13
For what its worth, I'm 90% back to where I was until everything flew all to crap. I understand 2 stroke from tuning snowmobiles over the years, always tring to get more HP.
1-It did seem to be a too rich problem but to have 3 turns from factory led me to believe it was another problem, so thanks for letting me know that wasn't uncommon.
2- The pinch at TDC with the plug out seemed strange to me as to where you don't see that in a snomobile engine, so that led me to think I scuffed a piston, which got me away from thinking it was too rich. Thanks for letting me know a slight pinch with plug out isn't that strange.
Its hitting 3rd gear pretty fast and alomst pulling whellies in the wet grass, I think its still a little rich on the HSN and could use a little tweak on the LNS and now raining to hard to keep tuning.
Again thanks for the help and quick replies. Rob
1-It did seem to be a too rich problem but to have 3 turns from factory led me to believe it was another problem, so thanks for letting me know that wasn't uncommon.
2- The pinch at TDC with the plug out seemed strange to me as to where you don't see that in a snomobile engine, so that led me to think I scuffed a piston, which got me away from thinking it was too rich. Thanks for letting me know a slight pinch with plug out isn't that strange.
Its hitting 3rd gear pretty fast and alomst pulling whellies in the wet grass, I think its still a little rich on the HSN and could use a little tweak on the LNS and now raining to hard to keep tuning.
Again thanks for the help and quick replies. Rob
Scrogg
Hardcore RCTalk User
No problem, you have to remember that there are no rings on the piston in these engines. Totally different way of making compression. Always just listen to the engine and give it what it wants.
