75 hp 2stroke Yamaha questions

[XpressHJ]

Lost compression on all 3 cylinders are 69 70 71 pounds. Blocks not scored, I was thinking either head gasket blew or my rings are shot.

Since I'm gunna be taking it apart what kind of mods should I do exhaust wise and head wise. I know I can start porting but want to keep it mainly stock for now.

Motor already has 90 jets and 90 reed stops. I was gunna cut the water bucket and the tuner but not sure what to do tuner wise.

Also should I run stock reeds or fiber?

Thanks for any help!

[Popa Sam]

I would suggest you start with a new compression guage. I've never known a motor with a problem to have compression that even.

[Jackson]

I would suggest you start with a new compression guage. I've never known a motor with a problem to have compression that even.

2nd that

[zul8tr]

And make sure the throttle is open full. After dry test add a few squirts of oil to the cylinderes and rotate crank to distribute the oil and take another compression reading. If much highere rings are good suspect.

[XpressHJ]

Ive tried 3 different compression gauges haha. Same on all three within a few pounds.

Ill try the wide open and oil.

I have sprayed BRP engine tuner into all 3 cylinders and let it sit over night as well. Came up a few pounds on all 3.

[zul8tr]

Since your initial compression readings were low and if adding oil still does not significantly raise compression in 1 or more cylinderes you might have stuck ring(s) in the piston grove(s). If this is the case try a good decarbonizer in the cylinderes and let sit for several days and add as it may leak out. Place engine in position such that piston crowns point to the sky and try place crank in such a position that the intake and exhaust ports are not open so the decarbonizer does not pour out. I am not familiar with BRP engine tuner.

[XpressHJ]

BRP Engine tuner is a decarb spray. I was told to do what you said to it but I didnt have time to let it sit. Im going to get another can then and fill up all 3 cylinders and let it sit.

Thanks for the info.

[Fast Fred]

brp moda tuna is the bomb:cool:

[Fast Fred]

never did see a difference for throttle open or closed on a 2storke, :eek: 4stroke for sure.

[zul8tr]

never did see a difference for throttle open or closed on a 2storke, :eek: 4stroke for sure.

I see a difference on my 2 stroke, but only about 3 tp 4 psi. Different engines different strokes?