May 5, 201511 yr Make sure the igntion is right, all the connections are tightly fitting and clean. Particularly the small wire connection to the coil. The wire that push fits to the coil (spade connector) can rattle/open up or get very mucky and cause issues when the bike moves, yet run ok when stationary. (I chased that one myself for hours) Now check through the fuel system. Check the carb carefully, that is has the right jets, that they are clear (same for the air bypass in the rear opening), that the enrichment circuit (choke) seals properly when closed, floats not punctured (rattle them to see if fuel has got in) and reset the height again, very carefully! Check the carbs balance tubes are free (most call them overflows, but they are to allow air in as fuel comes out) One on the bottom (float bowl) and one on the side (slide) Does fuel flow to the carb properly (blocked tap/fuel filter) from the tank, particularly when tipped up from the back (try main and reserve settings) and does the inlet valve to the float chamber cut it off when full? Check the intake rubber manifold for splits and cracks and that it's sealed to the engine properly, maybe the weight of the carb is opening a spilt up as the bike moves. Once you're sure all that is ok, it may be time to think about getting the engines ability to hold pressure tested (crank seals, head gasket) A two stroke specialist should be able to bung up the inlet and exhaust, than apply a small amount of air pressure via the plug hole. If it can't hold a few pounds, you've a leak somewhere, often a spray of soapy water shows from where! Edited May 5, 201511 yr by goudrons
May 5, 201511 yr It's a question of what changes when the rear is lifted. is there stress on the subframe that is moving the carb and opening an air leak in the intake manifold? Is lifting the rear flexing the frame enough to open the centercase gasket joint? Is lifting the rear causing some wire to contact the frame? Lots of questions. Maybe the place to start is the description. Is it changing the attitude of the bike that is making the difference or grabbing the rear and lifting. Does having the bike with the rear wheel placed higher that the front have the same effect as lifting the rear by the subframe? Since idle speed is affected I think an air leak is still prime suspect. Spraying a small amount of starter fluid will tell you if you have a leak in the intake manifold or the crankcase. Just spray a short burst at different locations around the intake manifold and crankcase seal (center case) and see if it changes the engine note. It shouldn't. If it does it indicates an air leak. Make sure all your case bolts are tight too as this happened recently to a friend. He had a couple of loose case bolts and now has a case leak just under the intake manifold. I doubt that it is a crank seal leak as that would normally not be affected by bike attitude. It is possible to have a case leak into the transmission which is being sealed by oil when lifting the rear of the bike. That's crying time as it a pretty sure case split to replace the center gasket but he's probably looking at that anyway.
May 5, 201511 yr Author At last! Been trying to reply all day but every time I log in and come back to this page I'm logged out again! (Home PC/Work PC/iPhone). Anyways, thanks, will pass the info on and see if we can find anything.
May 6, 201511 yr Just out of curiosity has this bike had its frame replaced? The '09s were notorious for cracking frames. I'm sure it has nothing to do with the problem but stranger things have happened.
May 9, 201511 yr My sons 08 rev3 did the same , adjust the floats slightly low. Fwiw I think it's all in the angle the carb sits at
May 9, 201511 yr Author I have a REAL hard time replying on this forum as it just won't stay logged in! Anyways, all info has been passed on, I think air leak test came up negative, pilot was incorrect so that's been changed and the float has probably been checked yet again. We're going out today for a few hours so we'll see if anything has improved.
May 14, 201511 yr I have faced this issue many times, and found it to be cured by a very detailed carb cleaning. In particular, removal of the tower that holds the jets and the clearing of the port (very small) that connects the outlet of the carb throat to the bottom of the tower. The port as I said is very small, and I use a number 79 gas orifice drill bit to clear it - am unsure of the metric size - and have in all cases had the problem solved. While in there clear all of the small ports and all should go well. I will post pictures for those interested in the next couple of days. Spencer
May 14, 201511 yr Author I have faced this issue many times, and found it to be cured by a very detailed carb cleaning. In particular, removal of the tower that holds the jets and the clearing of the port (very small) that connects the outlet of the carb throat to the bottom of the tower. The port as I said is very small, and I use a number 79 gas orifice drill bit to clear it - am unsure of the metric size - and have in all cases had the problem solved. While in there clear all of the small ports and all should go well. I will post pictures for those interested in the next couple of days. Spencer Pictures would be great!
May 18, 201511 yr Sounds like an intake air leak to me. The back of the frame is flexing causing an intake tube crack to open and close. I'd use brake cleaner and spray it all around the carb and intake. On my bike, just the smallest possible shot of brake cleaner under the carb and the bike stalled instantly. I found the center case gasket had blown out and it was sucking air into the crankcase. If the tail pieces on the frame are cracked or broken, the air box could be moving up and down, pulling the intake tubes apart. Dan's right about broken frames, I'd check the whole bike for cracks and breaks, loose engine mounts and anyplace that gets a lot of stress.
May 18, 201511 yr At last! Been trying to reply all day but every time I log in and come back to this page I'm logged out again! (Home PC/Work PC/iPhone). Anyways, thanks, will pass the info on and see if we can find anything. Have that sometimes, pressing log out and then log in again solves it here.
May 19, 201511 yr Have that sometimes, pressing log out and then log in again solves it here. I open the home page then the forums in a new window. Then log into the home page, and then refresh the forum page. Pain in the butt. I'm pretty sure it is because I refuse 3rd party cookies, but I'd rather log in twice then let websites set cookies in my computer!
May 19, 201511 yr Author I've tried all that but whenever I hit refresh it just logs me out again, regardless of how I navigate from the login page back to the forum/thread it more often than not just signs me out regardless, it's the sole reason why I hardly post here at all as sometimes it can take me 20mins to actually login! This is 100% not an issue on my end as its exactly the same on my home PC (IE and Chrome), my works PC (IE and Chrome) and my iPhone (Safari, Chrome and Opera)
May 19, 201511 yr Don't know how but I never log out one day to the next and always just pick up where I left off! Must be a nightmare.
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