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A Few Things Bothering Me


movingtarget
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So in the past few weeks I've had my bike out every night after a long break. Its an 04 rev3 270. Same problem with the spark plugs that I had last year, they seem to be building up with carbon and cutting out the engine every other night. I've been switching two plugs back and forth, just cleaning with a brass brush which makes them work fine again. I've been using exactly 75ml of oil(trials specific) to 5 litres unleaded with a good shake, NGK bp5res(maybe? definetly a 5 in there). I cant figure out whats causing this, I've replaced the cdi last year, and I have a spare stator which I could put in if I know thats whats causing the problem, trouble is I dont know... Also its hard to tell but there might be a knocking sound coming from the engine, this happened before and I had to get the small end bearing replaced, it was more obvious then but now its really hard to tell if I need to do anything about it. Every now and again it sounds a bit haggard, but then at other times it sounds smooth...

If anyone could offer any advice about these problems I;d be very greatfull, cheers!

Not riding comps due to location, mainly heathery hills, and rocky beaches, rock formations, rivers and BOGS. My gf's grandad also has a scrapyard full of ****** cars am eyeing up :rolleyes:

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If your riding mostly on idle jet for hours it will build up with carbon, sounds too rich as well possibly. Every half hour if your not reving much go up a hill a few times to clear the motor out on main jet or have a bit of a blast on the flat.

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Hi there,

This is not so easy to solve without looking at the bike, but here goes.

May be the carb is set too rich, choke on all the time, float height too high, bowl constantly flooding due to dirt lodged in the petrol needle valve.

Other less likely scenario's, oil seal passing on the clutch side letting in gearbox oil to the crankcase.

Cylinder bore badly worn - quite unlikely in the view of the age of the bike.

BP5RS plug is fine.

Might be a knocking sound.... is there one or not? If knocking under load then most likely a little lean, air leaking via crank seal on magneto side or ign set a bit advanced.

Sounding haggard - do you mean the motor is bogging down as if too rich?

Hmmm, so many problems.

Good luck.

Bye, PeterB.

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Thanks for the replys.

BetaRev3 -

Yes I have been doing that when the engine sounds bogged down or not responding quickly and it seems to sort it out.

PeterB -

I will try adjusting the carb needle although I've experimented with this a few times, I've done the carb mod which I found here last year, choke I switch off imedietly after start up,

'Other less likely scenario's, oil seal passing on the clutch side letting in gearbox oil to the crankcase.' This I have no idea about, will have to have a look, but not sure how or what to look for!

'Cylinder bore badly worn - quite unlikely in the view of the age of the bike.' The small end bearing was replaced last year after the bike got stuck in high revs after a crash it sounded fine after that. But this is what I'm worried about, something wearing.

By haggard I mean that knocking sound starts, but it is hard to tell. I might just be imagining things but I'm pretty sure it didnt always sound like that. It goes away under revs.

Thanks again

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I had similar problems with my old '03 Rev3... running rich, fouling plugs, strange engine knocking etc. It soon started to be extremely smoky and this obviously pointed to leaky crankcase seals.

Is there any movement in the crank shaft? If so, the main bearing may have gone and in my case it was this that trashed the seals.

Edited by neonsurge
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I had similar problems with my old '03 Rev3... running rich, fouling plugs, strange engine knocking etc. It soon started to be extremely smoky and this obviously pointed to leaky crankcase seals.

How can I check for this?

Is there any movement in the crank shaft? If so, the main bearing may have gone and in my case it was this that trashed the seals.

Would I check this by giving the flywheel a wee wiggle about a quarter through its cycle?

I've had the silencer off a couple times(once fell off while riding, dont ask!) it wasnt clogged but definetly quite gooey round the edges.

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Would I check this by giving the flywheel a wee wiggle about a quarter through its cycle?

The easiest way is to remove the flywheel, grab the end of the crankshaft and wiggle it around. If there's any play (no matter how small), your main bearing is probably gone or on the way out. It's not a terribly difficult or expensive job to replace but you will need to remove the engine and split the cases.

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