Pressure test = clutch leaking!
 

I'm still failing to get my bike running right.
I was hoping a straight needle (I replaced the N1EF with a DDJ) and stock (according to CPD) jets would help, but not so much.

So I tried a pressure test, but now I have questions...

The two vents:
http://www.gasgasrider.org/forum/pic...pictureid=1208http://www.gasgasrider.org/forum/pic...pictureid=1209

...were both blowing lots of air, so I plugged them them, but... Q1) are they detrimental air leaks during normal operation if left open?

Then, bubbles formed from behind the clutch slave. I checked the parts diagram and it doesn't appear that there should be a gasket behind it so I'm assuming something further in is leaking. Q2) what's likely to be leaking air in there?

I'm guessing whatever is leaking will require me splitting the engine to replace it. If so... Q3) what other stuff should I replace in my '01 engine while I'm at it? (the top end may have been replaced 10 hours ago, according to the kid I bought it from, ...who didn't do anything beyond changing the chain as far as I can tell)

I'm increasingly suspicious that there was an issue with the engine that caused a top end failure, and when they replaced the top end they decided to upgrade to a 300. They then did a terrible job of the upgrade (not getting the power valve connected correctly for one thing) and not fixing the underlying issue that caused the failure in the first place, and then gave up on the bike.

So, I'm expecting there's an issue to find that would cause a top end failure. Q4) would a bad air leak do that?

...and who knows what other bad workmanship. :rolleyes:

I'm so glad there's a place where people who know about these issues are willing to help us 2 stroke newbies! Thank-you everyone! :)

Link to Top End Rebuild and Top End Leak Down Test
 

Here is a link to my 2011 top end rebuild and leak down test.It might help.

http://www.gasgasrider.org/forum/sho...an+2011&page=2

Thank-you Moto7man! I had already found and read that thread, but in re-reading it I realised I had forgotten the bit about having the engine at BDC. I'll make sure it's set at that in the morning and try again. How does it affect the test not having it at BDC?

I sealed the exhaust port and was pressurizing (to 5 PSI with a bicycle pump) through the intake port, with the spark-plug still in. I had thought of going through the spark plug hole, but others on youtube were using the intake. Also I wasn't sure how/if the reed valve would effect the test; the air would be trying to go through it backwards, which I believe is what it's designed to stop. ...would it very slowly let air through (maybe making it look like a leak?); would it seal and not let the air through at all, which would mean the carb side of the reed valve wouldn't be pressure tested; or would be have no effect at all. I was unsure, so decided to play it safe, and go through the intake.

That's when I had no pressure due to the air going right out of what you refer to as the "powervalve vents". ...I'm glad I know what they're called now! :) So should either of those vents be left open when the engine is running? I know I had read that the bottom one is supposed to have a hose that is folded back to catch the run off from the vent (for safe disposal at some point). Is the top one the same? My bike didn't have a hose on the top vent when I got it, and the bottom one just ran up the side of the radiator and was open (not only that it had a split so it was spraying spooge onto the engine. :rolleyes:). I replaced that hose but haven't "folded" the end yet. Would having either/both of those vents open be an "air leak"?

Also, having stepped away from the issue for a few hours now, it occurs to me that I could (should) have checked the parts diagram to find what might be leaking. I just did that and I'm really confused now. Not only is the diagram for the clutch ...

http://www.gasgasrider.org/forum/pic...pictureid=1210

...layed out confusingly (I'm fairly confident that the slave cylinder is shown on the opposite side of the clutch than it actually is, which took me a while to work out), but I don't see any seals that might be leaking.

...and now I'm thinking about this more, the clutch area of the engine shouldn't have an open connection from the piston area, should it?!!! ...otherwise the transmission oil would be able to get into the engine. ...there shouldn't be any air pressure in the clutch to leak!! Oh bugger!! :eek:

Well, I guess that means the engine is coming apart, doesn't it?

I was just looking through the parts diagrams to put together a list of the items (bearings, gaskets and seals) that I might need for an engine rebuild and I noticed that I'm missing part 20 (the forth part in from the left) as shown on this page:

http://www.gasgasrider.org/forum/pic...pictureid=1211

It's the filter box air restrictor. However, that part isn't on the Central Powersports Distribution website's diagram for my bike.

If my bike should have that part it would likely explain it running badly. I had pretty much the same issue on another used bike I bought. The previous owner had cut the opening into the air box larger and then it wouldn't idle properly. Took me ages to work out the issue, but it ran great once I did!

Does anyone have that air restrictor on their bike?

...I'd really appreciate a photo and/or description of the holes in it so I can try to recreate it :D

It doesn't explain the air coming out from behind the clutch slave cylinder, but there's no reason to think there's only one (more) issue to solve on this bike.

I was thinking about this some more, and it occurs to me that there isn't a direct connection between the combustion areas and the clutch slave.

I tried looking at the parts diagrams to confirm this, but they were no real help. However, in this video (https://www.youtube.com/watch?v=RS6dtHwED1Y) a guy breaks down a 300 engine, and that was helpful. I'm very confident now that there's no direct connection.

I think the pressure must therefore be leaking through the right crankshaft seal into the clutch cover area (where the powervalve centrifical engager thingy-ma-bob is).

So to answer my own question, yes I have to split the engine and change the cranks seals. I assume I might as well do the crankshaft bearings while I'm at it, and probably all the other seals and bearings?

I'd still love to get some info on that air restrictor plate. And if anyone has any input on things I should/shouldn't consider changing while I have the engine apart, or even tips on things to do, or not do, to avoid making things worse I'll be very appreciative. :)

You should not have that air retrictor in your air filter box. It is only used for restricting the motor.

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Catching up with the thread I think you are getting there and I agree with above. Replace main bearings while you are in there. I put a rod in mine, but they are otherwise lowly stressed so might be worth risk to not if it looks OK.

Just want to agree with Anders, they may have had that restrictor in Euro bikes to meet emissions regulations (along with a catalytic converter in the exhaust pipe), but I don't see how it could run (and make any power) with that restrictor in there. IMO you don't want it!

Jeff

Thanks guys! That's both great and annoying. It's nice that not having that part isn't an issue, but it means I still don't know what the issue is. ...well apart from the engine leaking air. :D

I spent the whole day today tidying my shed ready for my big engine rebuild. ...I had to make space on my workbench, which require putting (or throwing) away all the important stuff (crap) that was dumped everywhere. I now have space!

I hope I'm getting there, this has been a very long journey so far (since September 15th, not that I'm counting the days), on a bike I thought was good to ride! :)

I had a growing suspicion that I should rebuild the lower end, so being forced to do it is not a terrible thing. I'm kind of scared of what I'll find in there though.

By main bearings do you mean just the crankshaft ones, or the piston ones as well (I'm guessing both)? What about bearings in the gearbox and clutch? and those seals as well? I don't really have a solid frame of reference as to whether anything is bad or not, so I won't be able to tell if I need to replace them. As such I was leaning toward changing them all, but I'm assuming that's going to be a lot more money, and extra work. :confused:

I'll check out the price of the rod as well. Hopefully, I don't need one of those though. This bike cheap is already no longer cheap. :eek:

Thanks :)