new2ypvs Posted January 24, 2010 Share Posted January 24, 2010 Hi I'm looking for some advice re. my 1987 RD350 YPVS F2. Before the worst of the weather hit us, I cleaned the bike down, oiled it, greased it, and dowsed in corrosion protector. But now, just a couple of weeks later, it starts (just) and then begins to make 'fart' noises from the left cylinder. After 30 seconds or so, dirty smoke comes out the left exhaust. Then it lets rip with an almighty backfire, accompanied by a small flame out the back. Then cuts out. I have checked the plugs are ok and clean. The compression seems fine, as with plugs out I can feel good pressure when the engine is turned. I've had the exhaust off to make sure there are no big carbon build-ups. Has anyone out there got any ideas for what to check next? Ta Matt Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 24, 2010 Moderator Share Posted January 24, 2010 Hi I'm looking for some advice re. my 1987 RD350 YPVS F2. Before the worst of the weather hit us, I cleaned the bike down, oiled it, greased it, and dowsed in corrosion protector. But now, just a couple of weeks later, it starts (just) and then begins to make 'fart' noises from the left cylinder. After 30 seconds or so, dirty smoke comes out the left exhaust. Then it lets rip with an almighty backfire, accompanied by a small flame out the back. Then cuts out. I have checked the plugs are ok and clean. The compression seems fine, as with plugs out I can feel good pressure when the engine is turned. I've had the exhaust off to make sure there are no big carbon build-ups. Has anyone out there got any ideas for what to check next? Ta Matt Right, first off there are better people on here for these but i'll give you my 2 peneth. The ig system is non adjustable and opperates BOTH cylinders with a wasted spark. So the coil and such are really proving themselves by the right cyl being ok. With the balance pipe the bike can (although badly) run on one carb, i'm not ruling a carb issue out but the fact that you get the backfire suggests there is fuel. Exhaust, neither here or there so long as it is clear. What happens if you swap the leads over i feel the problem may swap too, or possibly a plug. This is because to backfire the engine is igniting fuel that hasn't burnt and the only way that could really be happening is a weak or badly timed spark. I'm not ruling out other things, the doom mongers will shout crank seals which is entirely possible but to me this feels like a spark issue. Hope this helps........... Link to comment Share on other sites More sharing options...
new2ypvs Posted January 25, 2010 Author Share Posted January 25, 2010 Ok. So maybe swap leads/plugs to see if the problem moves. Cheers, I'll give that a go. What about the fuel-air mix? I had a sudden thought in the night that if the filter is blocked, then the mix ratio will be out. I wonder if this could be a cause? Time in the garage tonight I think. Matt Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 25, 2010 Moderator Share Posted January 25, 2010 Ok. So maybe swap leads/plugs to see if the problem moves. Cheers, I'll give that a go. What about the fuel-air mix? I had a sudden thought in the night that if the filter is blocked, then the mix ratio will be out. I wonder if this could be a cause?Time in the garage tonight I think. Matt If that was the case it would affect BOTH cylinders. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 25, 2010 Moderator Share Posted January 25, 2010 Also check cylinder head and base nuts are tight and exhaust manifold. Especially on the faulty side. Link to comment Share on other sites More sharing options...
new2ypvs Posted January 26, 2010 Author Share Posted January 26, 2010 Ok. So a swap of the leads, then a swap of the plugs gives the same problem, ie, dirty smoke from the left cylinder. I turned her off prior to the iminent big-bang as I'm sure its not a good thing to happen. Further investigation shows that both plugs are a touch oily. Added to that, the left exhaust is also more oily than the cleaner right one. Could this mean my piston rings are leaking? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 26, 2010 Moderator Share Posted January 26, 2010 Ok. So a swap of the leads, then a swap of the plugs gives the same problem, ie, dirty smoke from the left cylinder. I turned her off prior to the iminent big-bang as I'm sure its not a good thing to happen. Further investigation shows that both plugs are a touch oily. Added to that, the left exhaust is also more oily than the cleaner right one. Could this mean my piston rings are leaking? Nope, its a 2stroke the stuff on top is the same as the stuff underneath. Seeing as you have ruled out the ig nicely we can start looking elsewhere. OG has pointed out air leaks, has anything been disturbed lately. Noticed any damp or discoloured areas around the motor. I think its worth moving to the carb, its next easiest in the line, remove it without disturbing its neighbour any more than you have to and whip the bottom off, see whats in there then give the jets a lookie see. I use a bit of wire from a kitchen flex with the plastic off as a jet proder. Check the reeds are ok as well. Its a bit of a pain but if we keep it systematic then we will get it. Link to comment Share on other sites More sharing options...
new2ypvs Posted January 26, 2010 Author Share Posted January 26, 2010 I'm pretty sure nothing has disturbed or moved since it got put away. I have taken OG's advice and checked though, and all seems normal. A little oily perhaps, but I don't think its overly worrying ... yet. Before I take the carb off, are there any parts that I could replace whilst I'm in amongst things? Seals, gaskets, jets? It seems sensible to prepare whilst I can. Thanks for your help. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted January 26, 2010 Moderator Share Posted January 26, 2010 I dont know much about power valve bikes , i've only just got my first one and havent ridden it yet...however 'Cynic' does as he's had them before. What i'm wondering is this...Are there any seals connected to the rotating power valve or seals on the cover, the reasoning is that air can be drawn in through the breached seal giving the fart noises and explosions in the exhaust Opinions ? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted January 26, 2010 Moderator Share Posted January 26, 2010 I dont know much about power valve bikes , i've only just got my first one and havent ridden it yet...however 'Cynic' does as he's had them before. What i'm wondering is this...Are there any seals connected to the rotating power valve or seals on the cover, the reasoning is that air can be drawn in through the breached seal giving the fart noises and explosions in the exhaust Opinions ? Not seals as such OG, but there are O rings and bushes. As a rule though when they are leaking there is plenty of telltale black gunk to show. I did lose the clamp on my old 350 that links the 2 valves together, well lose, it more disintegrated i think. Long story, expensive memories, don't ever buy a race bike no mater how cheap. But that left the right cylinder with problems. Also OG do you think this has got to be a pretty big leak to stop the cyl, and its started all of a sudden. The only appeciable seal that could make a farty noise in the motor, (strange sentance) would a blown crank seal. But i don't want to go there yet. Lets prove the easier options first. Link to comment Share on other sites More sharing options...
new2ypvs Posted February 1, 2010 Author Share Posted February 1, 2010 Cynic and OG, thanks for your help with my RD problem. I decided to keep it simple and took the precaution of installing new plugs before getting into too much trouble with carb disassembly. I am not sure if I have solved the problem, or just masked it at this stage, but, as it goes, the bike is now running. Cheers Link to comment Share on other sites More sharing options...
Moderator Cynic Posted February 1, 2010 Moderator Share Posted February 1, 2010 Cynic and OG, thanks for your help with my RD problem. I decided to keep it simple and took the precaution of installing new plugs before getting into too much trouble with carb disassembly. I am not sure if I have solved the problem, or just masked it at this stage, but, as it goes, the bike is now running. Cheers Plugs and 2 strokes, bit like men and women can't live with. Can't live without. They can go in a heartbeat change em regular, some may say just like their women . Be worth a resistance check on the coil lead. Even check how good the spark is. Did you check the gap and condition of the old plugs, aside from the oil. Link to comment Share on other sites More sharing options...
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