Compression

[Upyourkiltbatman]

Did a enduro practice day Sunday and half way throught i stopped for a breather and when I went to start the bike again found it was hard to start and down on compression , rings are only about 20 hours of full on pace , is this all there worth or is there another problem , when it starts it seems to run ok , won't idle very well now though , 2011 300 .

 

[Jakobi]

Sucked dust?

 

[Upyourkiltbatman]

This wouldn't make it down on compression though ?

 

[nknudsen]

If your air filter wasn't seated properly it would by letting in unfiltered air.

 

[Jakobi]

The air filter itself wouldn't have an adverse effect. The particulates making their way through the engine would.

Has the bike been drowned at all? How many hours on the bike as a whole? When the rings were changed 20hrs ago how did the reeds look?

 

[memphis2857]

Sucking dust will make you lose compression quick, fast, and in a hurry! Think of dust as some really coarse sand paper being rubbed between your rings and cylinder walls


Sent from my iPhone using Tapatalk

 

[Upyourkiltbatman]

Not sure of total hours , I havnt checked reeds either , the bike is over running as well after full blast sections , I have pics of spark plug and piston , I have also got some strange oil comin out of cylinder

 

[Upyourkiltbatman]

Here's the plug

 

[Jakobi]

If the bike sucked a reed petal through the engine that could cause some potential issues.

Running on sounds lean.
Piston shows some blow by.
Plug is definitely not oily.

If it were me, and the engine has lost compression that it is noticeably felt at the kicker, and the bike is hard to start I'd be pulling it down.

Things you want to check are the air filter, intake boot where it seats against the carb. The manifold block between the carb and reed block, and the reed petals themselves. Also the flywheel/stator side seal. Once the head and cylinder come off the piston should still tell you more of the story.

Then depending on what you find as you pull it down will depend on how you go about fixing it.

Another quick crude check is to pull the cap off the carb and have a look under it. If its packed with dust/mud there is a sign that its pulled dirt through the intake. If not, continue down the path.

 

[Upyourkiltbatman]

Thanks for the input , will get out in the shed tonight and strip her down , cheers

 

[Upyourkiltbatman]

Can you do the flywheel seal without splitting the engine ? And is there anyway you can tell if it is ?

 

[Jakobi]

You can. Need to remove the flywheel and stator. If the seals shot there will likely be a load of oil built up around and below the seal. Get a pick into it and it'll pull straight out.

 

[Upyourkiltbatman]

Ok stripped her down and this is what I found , not sure why it has happened is it just failure or could it be my jetting , and what is the little hole in the cylinder wall ?

 

[memphis2857]

The little hole is a sort of compression release to make the 300's a little easier to kick. I have heard of some people epoxying them shut


Sent from my iPad using Tapatalk

 

[Upyourkiltbatman]

So anyone know what could have caused this ?

 

[Jakobi]

Niksasil be gone!

What else have you checked? Hows the piston look?

 

[Upyourkiltbatman]

Piston looks ok , but will change it and start fresh , took stator off and there is all crap around seal like dust sticking to grease/ oil , so this might be causing it to run lean . Got someone to do my barrel for ? 120 but should I get the compression hole filled in as well , it wasn't there before the coating came off ?

 

[Jakobi]

The 300 has the bleed hole above the exh port to help drop compression when turning the engine over by hand. It can't bleed enough to make a noticeable difference when the piston is moving quickly.

The leaky stator side seal could have been contributing.

More pictures, more digging, more info. I'd be apprehensive to put it back together without some kind of idea of what caused it or you could find yourself back in the same position again.

 

[Upyourkiltbatman]

Having the barrel re plated and the hole welded up , the engineer said the hole can cause the plate to start to go ? So replacing stator crank seal and hope that's going to do the trick , might even drop the needle clip down to the second setting , but was a bit boggy and smoky before , changed my needle from a n3eg to a n3ew not sure of the difference but going to give it a go

 

[memphis2857]

Hmmm the hole can cause the plating to go? I wonder about the other 10,000+ GasGas 300's out there with a bleed hole. Or what about the exhaust ports? Should we seal those up too to keep the plating safe? Do yourself a favor and leave the bleed hole


Sent from my iPad using Tapatalk