I picked up a TMX38 for 25 quid on eBay to try on my RB20. It goes like a rocket with it on - previously had VHSH 30. I'm running a seven7 manifold so it uses a plate manifold from Allens. Trouble is i just can't get the idle speed to come down to something reasonable. I'm running a 22.5 pilot, 325 main and 60 needle. I've tried smaller pilot (20) and gone bigger (up to 35) and it still won't come down enough. It just smokes with the bigger pilot. I've wound the airscrew in to about half a turn out and it will slow down but again it smokes and its spluttery. The throttle stop is wound all the way out. The carb is fairly old and the slide is a bit worn so could this be the reason? Could it be possible that the lean needle makes a difference? A mate has run the same set up but with a 58 needle.
I'm quite content that there are no air leaks on the manifolds etc as there were no issues before
Any suggestions?
Can't slow tickover down TMX38
I think I've convinced myself it is the slide as when I partially obscure the cutaway or press the slide inwards it does slow down. Strangely enough as I wound the throttle stop screw inwards (to raise the slide) it also slowed it down a little. Seems if you manipulate the slide in some way it affects it.
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Knowledge
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It could be that the slide-slot in the carb is worn too, and even a new slide will not redress the situation. I think you might have answered the question of why was the carb only £25. Before yuo give up hope, it might be worth trying to borrow a not-so-worn slide off a mate to see if this improves the situation.
The good news is that if you like what you have found (apart from the tick-over), then that £25 will help you decide to buy a good (new) TMX carb.
The good news is that if you like what you have found (apart from the tick-over), then that £25 will help you decide to buy a good (new) TMX carb.
Martin
I run a 38 on my RB260, with powerjet, so maybe not a great comparison.
Can never remember my carb settings, but will have a look if i can remember tonight and update
Can never remember my carb settings, but will have a look if i can remember tonight and update
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drunkmunkey6969
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I'd be interested to see the settings also, if you get chance. cheers.stokky wrote:I run a 38 on my RB260, with powerjet, so maybe not a great comparison.
Can never remember my carb settings, but will have a look if i can remember tonight and update
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I have a mate who has offered me his slide to try so thanks for that Martin. Maybe I'll have to shell out for a new one. I'd be interested to hear how the power jet carb runs on the RB. Someone suggested using a Thunder Power Jet from the US. They are easily adjusted by a knurled knob. Not heard of anyone using one though.
sorry forgot to get details last night, will do tonight
However one thing I do remember is that there are 2 TMX38's, with differnet inlet side opening sizes.
The smaller one is what I have, as its exactly the same opening as the dellorto VHSA32, Dellorto VHSB34 and TMX35 (and hence fits all same manifolds and rubbers etc)
You might just want to measure, so we are all using and talking about same one
Always keep asking myself, if inlet opening on all these carbs is the same, does it make much differnece the mouth size ??
However one thing I do remember is that there are 2 TMX38's, with differnet inlet side opening sizes.
The smaller one is what I have, as its exactly the same opening as the dellorto VHSA32, Dellorto VHSB34 and TMX35 (and hence fits all same manifolds and rubbers etc)
You might just want to measure, so we are all using and talking about same one
Always keep asking myself, if inlet opening on all these carbs is the same, does it make much differnece the mouth size ??
sorry for any delay in replying..............but here goes
I actually have a TM38 flat slide on my RB261 (not a TMX).
There are 2 version of TM38, with different inlet side openings (43 and 47ml)
I have the smaller 43m one, as fits will all manifold and rubbers same as a TMX35 or DO 34
Have found an old Dyno sheet for it, so carb setting taken from that :-
Has a PowerJet (think size is 30, but not written down)
Main Jet 300 (but remember you downsize this with PJ)
Needle is P4.5
Atomise Q-4
Pilot 27.5
You might also find a company called Niche Cycle useful, they supply all the 2 stroke dirt bikes with Mikuni's in the USA, really good at answering email questions about these carbs.
On all my Mikuni's I find the tick over adjust screw has more variation than DelOrto's
Finally was messing with another scooter other night (mikuni TMX35), and tick over went mad on that, all it was, was cable outer came out of the metal holder on top of carb (simple but worth checking)
I actually have a TM38 flat slide on my RB261 (not a TMX).
There are 2 version of TM38, with different inlet side openings (43 and 47ml)
I have the smaller 43m one, as fits will all manifold and rubbers same as a TMX35 or DO 34
Have found an old Dyno sheet for it, so carb setting taken from that :-
Has a PowerJet (think size is 30, but not written down)
Main Jet 300 (but remember you downsize this with PJ)
Needle is P4.5
Atomise Q-4
Pilot 27.5
You might also find a company called Niche Cycle useful, they supply all the 2 stroke dirt bikes with Mikuni's in the USA, really good at answering email questions about these carbs.
On all my Mikuni's I find the tick over adjust screw has more variation than DelOrto's
Finally was messing with another scooter other night (mikuni TMX35), and tick over went mad on that, all it was, was cable outer came out of the metal holder on top of carb (simple but worth checking)