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Stalling On Downhill


luckaz
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  • 1 month later...

Wanted to give you an update. The mod did not work. Still stalling. I changed the float height so much that eventually the bike wouldn't start; still stalling. Tried moving to a 50 pilot jet; nope.

Any advice? I'm frustrated. Just want to sell the bike now and get rid of this problem. Our local trials mechanic is just as baffled as me. He has same bike and same problem.

Thanks

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Luckaz,

To be honest, we have no idea your level or ability, just how extreme downhills you are referring to. There are limits it seems on any carb or bike, yet in my opinion the K carb is more susceptible as compared to say a stock Dellorto.

Splat Chris would be the uppel level rider with better answers, yet I can tell you from many bikes past, I had to anticipate a fuel surge on big downhills and clean out as necessary.

MC

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It has nothing to do with 'extreme downhills'. It will stall going down fire roads or logging roads that a typical truck could drive up. We have loads of steep riding here but it will stall on stuff you could ride a bicycle up.

Thanks for any suggestions.

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Thanks Charlie,

I'm considering a new carb just to see if that could fix the issue. Easy way to sort out the source of the problem too.. If it still happens w a new carb than the carb is unlikely the cause..

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Other than a few reported issues with setting of the float levels, I cannot recall sig. reports of issues such as yours. There may be a possibility the float is hanging up in the overflow tube that extends up into the bowl. Such radical changes in float height are generally not needed.

I pull the overflow tube and BB it off on a K style carb, myself. Splat Chris has some suggestions of that on his website, yet all personal pref.

I say all this while still using the Dellorto on my 250, which just works it seems. Nothing special, not as great o power or all that, just works.

Call Chris and debate it! He gives sound advise and better experience.

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  • 1 month later...

Just wanted to let anyone who is interested know that increasing the idle speed fixed the problem. Embarrassing to admit and a huge waste of time in retrospect(taking the carb apart ~ 15 times). Simply increasing idle speed fixed it right away. Thanks for all your suggestions.

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Just wanted to let anyone who is interested know that increasing the idle speed fixed the problem. Embarrassing to admit and a huge waste of time in retrospect(taking the carb apart ~ 15 times). Simply increasing idle speed fixed it right away. Thanks for all your suggestions.

Good report then, yea, keeping it jacked slightly is good! Regardless of carb, I set mine to where the bike will chug up a slight grade in 2'nd on its own.

Ignition timing comes into play as well, specially on some prior year models, as they may kickback stall at low revs if too advanced,usually at the wrong time!

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  • 6 months later...

Just to dig out an old thread, i also just upped the idle speed to mask the problem. However after a while the idle on mine also became erratic. It turns out the rubber on the inlet manifold starts to dry and shrink over time, peeling itself of the metal core and reed block. Stripped the inlet manifold and reed block, re-sealed with engine gasket sealant.

Back together and it is a revelation! It must have been getting slowly worse and worse and i hadn't really noticed. It's like a new bike, lovely and smooth off the bottom, no hunting, and no stalling on steep descents, even with a very low idle. I think the stalling on steep descents was down to the weight shift of the carb, opening gaps and ruining the mixture.

I spoke to Chris at splat shop, and confirmed all the above, apparently he's seen it a few times, and has re-sealed a few inlet manifolds. Wish i'd rung him sooner, bloody top bloke.

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Brilliant Cord, I'll have a look at that area asap. I recall I had to put some tape on the Carb outlet previously as the boot was a bit loose. Maybe there is more going on there that I missed.

Thanks

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So I took the reeds out and found the gasket material there very slightly crinkled (not cracked) . There was a little discolouration where it looked like gases were escaping or being sucked in. I cleaned everything and sealed it all with a tiny amount of silicone. I rode today and for the first time the bike didn't stall once. Couldn't believe it. Finally found the problem. Thanks

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So I took the reeds out and found the gasket material there very slightly crinkled (not cracked) . There was a little discolouration where it looked like gases were escaping or being sucked in. I cleaned everything and sealed it all with a tiny amount of silicone. I rode today and for the first time the bike didn't stall once. Couldn't believe it. Finally found the problem. Thanks

Are you referring to the outer(rectangular) reed block sealing surfaces?

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