Engine Trouble The sound of 4 stroking?

[Carl Walichnowski]

As a noob I have no idea what it sounds like when a motor 2-cycle motor 4-strokes. I have engine troubles I've been attempting to get assistance with and I've been asked if the motor 4-strokes?? Well I wish I could answer that but I have no idea what that actually sounds like. Does anyone have a link I could refer to that would possibly show video of a motor 4-stroking???

 

[crassius]

usually, whenever it is not making that ring-a-ding 2-stroke sound, it is 4-stroking

this is not always bad if it does it other than under load

 

[Carl Walichnowski]

Well the sound difference is not technically my concern but the fact the bike is running about 20 mph slower then it should be and I'm trying to troubleshoot the issue. my next step is to do a compression test (it should be around 135-150 correct?) and also lower my jet size to tune the carb. If it is actually 4-stroking and I can verify the sound that could possibly assist forum members in helping me fix my engine problems.

 

[gary55]

2 strokes fire every revolution. Four stroking is when the mixture is to rich so the engine only has enough oxygen to fire every other revolution. So it sounds like it is only firing half as often as it should, and delivers half as much power in a given time. I still think you will find the compression low, but that is just a guess.

 

[Frankenstein]

Please swap out that head gasket, I would bet that reused spare is causing the problem or at least half of it...

 

[Carl Walichnowski]

Please swap out that head gasket, I would bet that reused spare is causing the problem or at least half of it...

Oh I will be swapping the head gasket, I'm ordering the .4 & .6 mm copper ones tonight from BMW, I was just waiting for them to reply to my email about providing that sliding carb needle with the order. Don't worry Frankenstein Young Grasshopper listens well.

 

[Carl Walichnowski]

2 strokes fire every revolution. Four stroking is when the mixture is to rich so the engine only has enough oxygen to fire every other revolution. So it sounds like it is only firing half as often as it should, and delivers half as much power in a given time. I still think you will find the compression low, but that is just a guess.

well that's what I think is happening then. The best way I can put it is the tone or height of the sound doesn't change only the consistency of the sound of the motor. It also doesn't happen at any specific point in the power band and it seems more random then anything. I never used a compression tester but after a bit of google searching I'll do a compression test to see where the compression is, where should it be between 135-150 psi? Also is it bad for the motor to 4-stroke? Can I continue to ride my bike without damaging the motor until the head gasket arrives?

 

[Frankenstein]

well that's what I think is happening then. The best way I can put it is the tone or height of the sound doesn't change only the consistency of the sound of the motor. It also doesn't happen at any specific point in the power band and it seems more random then anything. I never used a compression tester but after a bit of google searching I'll do a compression test to see where the compression is, where should it be between 135-150 psi? Also is it bad for the motor to 4-stroke? Can I continue to ride my bike without damaging the motor until the head gasket arrives?

Yes absolutely it's safe, it's safer than 2 stroking..

 

[gary55]

Ya I don't see it hurtin much. Might want to throw a spare plug in your pocket and park it over a piece of cardboard. Things may get as Steve says a little spoogie. 135 to 155 is about right. Can't wait till you test it with a new gasket. Then we'll know if it's a 6cc or 8cc.

 

[Carl Walichnowski]

Ya I don't see it hurtin much. Might want to throw a spare plug in your pocket and park it over a piece of cardboard. Things may get as Steve says a little spoogie. 135 to 155 is about right. Can't wait till you test it with a new gasket. Then we'll know if it's a 6cc or 8cc.

Well I wanted to take the head off and go back to the stock to see if tha was the issue and while tightening the studs back down I noticed two of the studs continue to spin regardless how much I tightened them? Now my son torqued down the head prior so I'm not sure if they were like this but do you think they are stripped? If so can I rethread them?? I'm thinking this may of been a reason, along with the reused head gasket, for potentially weak compression, what do think and how do I fix it? HELP!!