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Tr34 Idle Speed Vs Choke?


timo99
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Hi Guys, first time poster. Wondering anyone can help me out with my bike.

It's a 1992 or '93 Beta TR34 260cc Alp, Long Range. It's air-cooled, Dellorto PHBL, upside down forks. Got the bike from an old riding buddy later this summer and it was sitting in a barn for who knows how long.

First thing was to tear apart the carb and replace o-rings, gaskets etc. After getting it all together and fresh premix it fired right up and ran "pretty good". Played around with the fuel screw and idle and it always revved high. Not an air leak type of high rev, but way too high. Especially after going down my dead end road and the tractor path to the woods (up to 4th-5th gear).

Opening the choke (up) always clears it up but then when you put it the choke back (down) the revs kept climbing. Made for a really awkward woods ride. Lurching -not smooth and steady.

By accident left the choke up and it rides quite perfect. Nice and slow idle with throttle control right where you'd expect, in fact its quite awesome in the woods.

Wondering if this is by design? Since the bike has lights, horn and brackets for passenger pegs was it a dual setting (rich/lean) for road and woods/trials?

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I had also some problems with adjusting the carb. My TR34 replica from 1988 had no bottom and the idle rpm changed from being to low or to high.

An comparison with the original specs for needle and jets showed that there were a different needle and a different main jet used, additional the slide was worn and too the small gaskets for the air screw, at least the idle jet was too clogged. I replaced the jets, valve, needle, slide and air screw with gaskets and voilá all issues to the carb were gone. You never know what has happened to all these small parts during the last 20 years, in doubt as they are not expensive replace them. If the bike then run very well you have fixed the issue. If not take a look at the rubber manifold of the intake the rubber can have cracks ( mine had), it's also good to take a look at the reeds they too can be worn out.

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  • 1 month later...

Hi Guys, first time poster. Wondering anyone can help me out with my bike.

It's a 1992 or '93 Beta TR34 260cc Alp, Long Range. It's air-cooled, Dellorto PHBL, upside down forks. Got the bike from an old riding buddy later this summer and it was sitting in a barn for who knows how long.

First thing was to tear apart the carb and replace o-rings, gaskets etc. After getting it all together and fresh premix it fired right up and ran "pretty good". Played around with the fuel screw and idle and it always revved high. Not an air leak type of high rev, but way too high. Especially after going down my dead end road and the tractor path to the woods (up to 4th-5th gear).

Opening the choke (up) always clears it up but then when you put it the choke back (down) the revs kept climbing. Made for a really awkward woods ride. Lurching -not smooth and steady.

By accident left the choke up and it rides quite perfect. Nice and slow idle with throttle control right where you'd expect, in fact its quite awesome in the woods.

Wondering if this is by design? Since the bike has lights, horn and brackets for passenger pegs was it a dual setting (rich/lean) for road and woods/trials?

Sounds like you're running lean on the pilot.

I've got a 93 Supertrial, basically the same bike. 240 motor. Same lights, horn, and brackets for passenger pegs.

Double-check the carburetor. Mine has a Dellorto PHBH, not a PHBL, and it'll clog the pilot jet if I even look at it funny. Difference is air screw versus mixture screw. Drop the bowl on the carb, pull the slow jet, and run a fine piece of copper wire through it. When the pilot gets partially clogged, mine has exactly the same symptoms as yours.

Whereabouts in upstate NY are you? I'm just outside of Troy, and hoping that the snow will melt in the yard in the next few days. Got some riding in last weekend, but we've been socked in with snow since Tuesday. :wall:

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