701 Cylinder Cracking??

[dirkdiggler]

What Exhausts are best known for Cracking the cylinders on Yamaha 701 motors???

I am Using a Pro-Tec Exhaust on my Superjet........It has a bracket that mounts to the middle mount on a stock cylinder head.

Does the aftermarket exhaust being mounted to the top of the cylinder head increase or decrease the chances of cracking a cylinder ???

 

[Kaveman]

Just about any of the AM exhausts have the potential to crack a cylinder on the intake side if you are riding hard (jumps, rolls, hard landings etc.) The ADA girdle kit stops this due to the way it sandwiches the cylinder rather than bolting it to the cases and the head to the cylinder.

 

[dirkdiggler]

has anyone cracked a cylinder with a stock exhaust?? The pipe in my pic bolts up too the same location as a stock exhaust....??

 

[WFO Speedracer]

has anyone cracked a cylinder with a stock exhaust?? The pipe in my pic bolts up too the same location as a stock exhaust....??

701 cylinders can crack at any time and without any reason,large exhaust pipes and higher compression heads make the problem worse.

 

[dirkdiggler]

Do you think that by mounting the exhaust to the head(In the pic) it will reduce the chances or increase the chances of cracking?

 

[Waternut]

Well I've thought about it from multiple perspectives and I highly doubt that mounting it with that damper will have any real affect on the cylinder cracking. A simple rogue flaw or tooling mark in the metal of the cylinder will create far more problems than mounting the pipe to the head.

It could make it more prone to cracking based on the fact that some of the weight/vibration is being applied at the top of the cylinder as opposed to the middle. Then again the damper itself could help reduce cracking because it distributes the load.

Bottom line is...if you're really worried, get a half girdle kit and be done with it. Otherwise, leave it alone and take the chance. Just remember a hot cylinder is softer and will be more prone to cracking than a warm cylinder. They are quite a few people that have never had a problem. There are others that break motor mounts, cylinder, etc. doing basic stuff.