This is not minibike related but I couldn't get any responses in the sled forums so I thought I would ask here. I recently put a 200cc clone into my young fellas arctic cat 120 mini snowmobile and when I did it it had tons of power, it would spin the track with me (200lbs) and take me to 20mph. Now after approx 10 hours of use it will barely take my son (50lbs) to 14mph and won't make it up hills with him. Throttle is operating fully and the choke is off completely and I also tried removing the air cleaner with no change. I did a compression check and it is only showing 70psi and with 2 teaspoons of oil in the plug hole it is showing 85-90psi. There is no burning oil smell at all. Could this be a valve clearance issue? When I removed the govenor I made up some shims for the valve springs from washers approx 0.70" thick for more spring pressure and re-adjusted them to factory specs, could 1 or both of them come out of adjustment or something. I assume if the rings were bad I would be smelling burning oil. Thanks for any help
Well I took the engine out and the valves were both approx. 0.10" so I readjusted them to 0.03" ex and 0.02" intake. Then I rechecked compression and it fell to 40psi ????? I removed head and everything looks good, no burnt valves, everything nice and smooth, no scuffing etc.... I then noticed the decompression system on the cam gear, will this give me false readings when checking compression? I am using the electric start while checking and it is turning over fairly fast. It always needs choke to start no matter how warm it was and it idled good just didn't have the take off or top end it did. Plug is nice and tan color, I will check carb for dirt and clean it, there is only a total of 10 hours or so on this engine. I'll check flywheel as well.
Valve lash should be .003 not .03...
The reason I said to relap the valves is it should be done right way from the get go...alot of these clones do not seal well from the factory.
A tan colour on the plug could mean a carb issue...usually the clones run rich and always show a black plug.
And yes the compression release will give you a false reading.
The reason I said to relap the valves is it should be done right way from the get go...alot of these clones do not seal well from the factory.
A tan colour on the plug could mean a carb issue...usually the clones run rich and always show a black plug.
And yes the compression release will give you a false reading.
The compression does test low on engines with a compression release. In fact, Briggs & Stratton's recommendation is to not check the compression but instead perform a cylinder leak down test. The leak down test is the only way to go, it gives you the answer.
Have you checked the clutch? Have you checked for extra drag in the drive train? Brake hanging up?
Have you checked the clutch? Have you checked for extra drag in the drive train? Brake hanging up?
I did a leak down test and was showing 10% leakage and the air was coming from the intake. I lapped the valves and now it is only showing 4%. I set the valve lash and am still not getting the power it had when new approx 10 hours of use ago. This is driving me crazy. I did not check the flywheel key yet, to do so I would have to remove the engine again, I can't see how would ever shear it but if it did would it still idle perfect and just not have the high rpm and power it should with no govenor? We ran it today for about an hour mostly wide open with a new plug, the plug stayed is perfectly clean. I tried running wide open and slowly pulling out the choke and it just got weaker. Any other ideas
Make a piston stop from an old spark plug and find TDC.
Measure the circumference of the flywheel and divide by 360 so you know how many mm per deg.
Put a mark on the flywheel at TDC and where you suppose the factory timing should be ( around 20-25 BDC ).
Time it by light and set it for 25.
No key needed.
Lap the flywheel and bolt it on ( using piston stop to hold it in place as you set the wheel )
Now when you tell me it does not have the RPM and power it did 10 hours ago and you had to lap your valves is it possible you have revved the living shite out of this and floated the valves?
You may have in that case softened up your valve springs to the point where it can't rev and they need to be replaced.
I would not over look that possibility.
The 18 pound spring is from a G200 honda flat head.
No governor and these springs, you are playing with dynamite!
Ignore the factory lash setting and set them by feel for as close as possible to zero.
sometimes there are tight and loose spots on the cam lobes where the feeler gauge is lying to you ( especially true of cheap clones with bad lifters, is this a blue WASP perhaps? )
Those garbage Chinese plugs are good for something.
Knock the guts out and make one of these to help you time your clone.
Its just the plug shell with a 3/8 Hilty stud but any bolt will do.
Measure the circumference of the flywheel and divide by 360 so you know how many mm per deg.
Put a mark on the flywheel at TDC and where you suppose the factory timing should be ( around 20-25 BDC ).
Time it by light and set it for 25.
No key needed.
Lap the flywheel and bolt it on ( using piston stop to hold it in place as you set the wheel )
Now when you tell me it does not have the RPM and power it did 10 hours ago and you had to lap your valves is it possible you have revved the living shite out of this and floated the valves?
You may have in that case softened up your valve springs to the point where it can't rev and they need to be replaced.
I would not over look that possibility.
The 18 pound spring is from a G200 honda flat head.
No governor and these springs, you are playing with dynamite!
Ignore the factory lash setting and set them by feel for as close as possible to zero.
sometimes there are tight and loose spots on the cam lobes where the feeler gauge is lying to you ( especially true of cheap clones with bad lifters, is this a blue WASP perhaps? )
Those garbage Chinese plugs are good for something.
Knock the guts out and make one of these to help you time your clone.
Its just the plug shell with a 3/8 Hilty stud but any bolt will do.
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I was thinking something along those lines about the valve springs losing their strength, I have a set of 18lb one on order. Before I dive into the timing issue (which will involve removing engine which is a PIA) would it give my symtoms, as I understand it doesn't it give you more in either high or low RPM, I have lost power in both. Maybe I will wait for the springs and if they don't solve my problem then I will look into timing. I built my leak down tester using an old plug like you did, I tapped the inside to 1/8" pipe and screwed in a barbed fitting for the hose.
But what does floating do? Prevent higher RPM or risk hitting the piston?
I have all the tools, it is that the engine sits in the chassis right next to a bulkhead and even if you could get the flywheel cover bolts out you would never be able to move the cover away from the engine. Plus no room for impact gun, puller or hammer.
I have all the tools, it is that the engine sits in the chassis right next to a bulkhead and even if you could get the flywheel cover bolts out you would never be able to move the cover away from the engine. Plus no room for impact gun, puller or hammer.
OK, I just received my new Honda 18lb valve springs (G200 part) and installed them and nothing, no improvement at all, I can't describe how frustrating this is. One thing I noticed is that with the valve cover off the exhaust valve operated twice as fast as the intake while I am turning the engine over with the electric start, I assume this is supposed to happen with the decompression system built into the exhaust cam. Is there a chance the mechanism is malfunctioning and this decompression thing is not releasing at higher rpm like it should. Mechanically the engine is perfect, I moved the exhaust rocker arm off to the side to check compression and it is 155psi and there is less than 4% leak down. Tried with exhaust removed, air cleaner removed. I even tried running wide open and dripping extra fuel into the intake and it just stalls.
