Ok , basically the bike was running funny, started and run fairly ok with the choke on, take the choke off, the revs go high then dramatically drop down and then cuts out.
the idle speed screw was abit mashed on my carb and couldnt get it out, so recently i bought a 2nd hand carb and fitted it, exactly the same problem.. ?
Now im confused , the reed valves are fine, there is no air leaks that i can see or feel
iv sorted the white dt's problem like this by sealin all the manifolds an an gaskets up an just using it a lot it just went away its only done twice since an both times that was cos the tank was empty or just a drab left swishin about
Unfortunately you cant check the seals. The only way is to replace them which is cheap enough if you are able to do the work yourself. Based on what youve said you've changed (pretty well everything) that would be my recommendation. Crankcase compression is critical on a 2 stroke. Good luck and let us know how you get on.
To save a long post I'll assume you can take off the flywheel and ignition backplate on the left side and the water pump pipe, clutch cover, clutch and engine pinion on the right. You'll need a sharp tool to dig out the old seals and as you are levering them out be careful not to damage the crankcase or the crankshaft. The left one should be easy, the right hand one is a little more difficult as it is a double sided seal. When you come to push the new seals in, smear oil over the crankshaft to protect the lips of the seal as you slide it on. Make sure you push it on square then get a large socket or something that is just slightly smaller than the outer diameter of the seal and gently tap it home until flush with the crankcase. Again, make sure that the drift you are using doesnt damage the lips of the seal. Good luck and hope this helps
There's, a sticky on this part of the forum with part numbers from simplybearings.co.uk. They are about the cheapest. You should be able to buy off ebay as well and the seals are different each side.
That's not a happy motor. Sounds like its running very, very weak, even with the choke on. My best guess is crank seals, based on the fact you have changed everything on the inlet side of the engine. I'm also assuming that there is a good flow of fuel into the carb. My only concern is that you say that it starts ok. Normally, when crank seals are worn, starting is a problem.
Something you could check - is the gearbox breather. I've never done this before but it should give you an indication. Despite my earlier post about not being able to check seals, give this a go. Put your finger over the end of the breather pipe to block it off and see if that changes the running of the engine. If it does, you've found your problem in the right hand seal. if it doesnt, then just try changing the left hand seal - which is the easiest to do anyway. If that doesnt change anything then its time to scratch heads and have another think. By the way, I couldnt open the 2nd youtube vid.
Ok i have the hayes manual too , where can i find how to change the crank seals because i seriously dont know how too , also which breather pipe do you mean ?
The breather for the gearbox is just in behind where the tacho cable connects to the gearbox when you look at the engine from the right side.
Changing the crank seals will require a special tool - a puller to get the flywheel off. If you havent got it then probably best to give it to a local motorcycle shop who has the equipment. I doubt if the Haynes manual will describe changing the seals without a complete engine strip. The parts that are relevant though are chapter 1 sections 8, 9 and 14. This will get you to a point where the seals are exposed and they can be dug out as per my previous post.
No, upper cylinder compression is not affected, but you need to maintain a sealed crankcase and crankcase compression. What happens is two things. On the downstroke of the piston a small amount of pressure builds up in the crankcase until the transfer ports open. This pressure of fuel/air mixture can leak past worn seals and the lower pressure reduces the speed and amount of the mixture transferring into the cylinder. The second and bigger problem is that on the upstroke fuel / air is drawn from the carb but also air is drawn in through the worn crank seals which weakens the mixture, which is what you can hear on the youtube video. 2 strokes sound very different when they are running weak - they sort of "run on" and the exhaust note gets a lot softer and there is no "crackle".
Hows that for an old man rambling on eh? "In my day...." lol.
Flywheel extractors are available on ebay, just check which flywheel you've got. The later flywheels have got a big thick disc riveted to the front which needs a flat plate with two attachment bolts and a jacking bolt. The early ones need a puller which is basically a tube with an external fine thread and a jacking bolt going through the middle. If you have the later flywheel message me your address and I'll post you the puller to borrow.
