101 carb questions

[SpookDog]

Can anyone tell me what year the 28mm was introduced? Did the 26mm get used up till 96?
Has anyone else ever fitted a 28mm flatslide to an early 26mm roundslide bike?

I apologise in advance cause I have probably more like 1001 questions.

My bike has never run properly. I have a 28mm flatslide that came with a 180 main jet. I recently changed it to a 210 and the bike wouldn’t run above 1/2 throttle! I was ‘read’ to believe that the main jet only affected the last 1/8 of throttle? That the bike should still run fine even without a main jet, up to 3/4 throttle?...

Also, when I let the throttle off at certain revs/speeds/throttle position, the engine actually picks up and accelerates! I’m guessing I’m gonna have to go back to square one with this. The head gasket is fixed with an Athena gasket, the bore and piston are sweet. I’m gonna check again for inlet air leaks. But if anyone has had these problems before, or has insight? Help!! 🤪

[declan]

@spookdog wasn't the 26mm pre 88? I have a Kehin 26 on the dtx bike I'm building

[declan]

Are you sure your carb is genuine? Can you show me a picture

[SpookDog]

@declan @declan @declan
VM26SS (roundslide) was used in early bikes, I think till 97 but ain’t sure...

My carbs’ a 28mm Mikuni flatslide. It’s genuine. It has the heater pipes...

A 2004 onwards DTX125 should have a 28mm Mikuni TM as well. According to my Haynes...

[declan]

@spookdog that can't be right you rarely see a 26mm dt plus mine is a 1990 and was flatslide,180 main seems very lean I'm 210 on my 28,it's not burning gearbox oil is It?

[markus.w]

@spookdog the 26mm round slide was used in the very early 88 models only.

[SpookDog]

Cheers guys, it’s confusing cause it says vm26ss 3rn1 onwards in the Haynes. I’m guessing they messed it up. It’s been throwing a spanner in for a while now! 🤨

I’m guessing the 3rn1 onwards should read tm28? Did the TZR use a 26 or 28?

[declan]

@spookdog I think 26

[SpookDog]

@declan
I only ask cause the Haynes says the TZR uses a 180 main jet. I’m wondering if a previous owner thought a ‘TZR’ main jet would be a good thing...

I know the engine is good. I’m gonna put the 210 main and .225 pilot in all according to specs. Q2 needle valve and 5j25 needle. Make it standard for a TM28SS carb...
If I still have problems with anything above 1/2 throttle I’ll adjust the needle height. I don’t know what else to do. I’ve swapped out the reeds and cage to no improvement...
Wish me luck

Any opinions or advice is welcome...

[declan]

@spookdog check your ignition circuit the whole thing from killswitcg to spark plug look for any corrosion or breaks in wires

[SpookDog]

Anyone good at reading plugs?...

[SpookDog]

The centre is usually a good colour, but it is only the very centre, electrode, ect. The ‘outer ring’ is always black and wet. No matter how it’s ridden. I removed the bottle top plug I have on the carb to filter rubber, to let more air in and the engine ran a lot better. Not proper but better...