M88 tune up - nozzle question

[David V]

I've just cleaned the M88 carb on the WLA and changed the cork float for a rubber ducky one. The bike was running really rough recently. A lot of deposit in the fuel filter.
The bike revs quite smoothly but I still have a bit of a rough spot at low throttle - I guess this is what you would call the "tip-in" spot.
Reading the Linkert manual from Victory publishing this weekend, he suggests drilling a tiny 1/32" hole in the main nozzle just above the venturi to help or to drill a tiny 2/32" hole in the throttle disc.
Has anyone tried this kind of stuff out ?

David V

[1stCAVREG]

I have not tried drilling the main nozzle or disc. However, since you have a flat spot at low throttle, I would look for a problem within the carb and not try correcting by making alterations. The alterations will, at best, mask the problem which will still be there.

You may have a clogged idle passage. I would also look at the little top hat shaped piece that sits between the body and the low speed needle's spring. That piece and the needle should not be allowed to be too worn. Too much clearance will allow in too much air for a proper low speed mixture. Too little clearance will not allow enough air in for the low speed air/fuel mixture.

Also look at the throttle disc where it meets the bore at the top of the disc for wear in both the bore and the disc. Being too worn will make it difficult to obtain a good idle.

[David V]

I thoroughy cleaned all the passages so I'll rule that out.
The throttle disc is in the right place and I really spent time checking this because I had replaced the throttle shaft - although the disc is not new.
I'll check out the whole low needle assembly. I had replaced the lever spring collar on it a few years ago because the thread was worn.
I know the needle is a bit worn but I tried putting a new one in and the results were worse so I figured the needle and body must be worn together so best to leave them like that.
No-one's played around with the main nozzle ? I'm surprised.
Anyway, weekend coming up so there will be time to play !
Thanks

[steveale]

david, also search somee of the threads on caimag.com and hydra-glide.com common problem symptom at both high and low speed is intake leaks. seen pressure bubble tests cure a lot of peoples ills...more often than not.

[David V]

If the venturi is a bit loose would that also affect low speed thottle ?
I came across a German company last week that make venturis with O-rings in them to eliminate any leak.
They also make a "bomb-sight" venturi for the Linkert.
Anyone try one of those ?

Thanks for the links - I'll check them out.

The bike's running pretty smooth this w-e after resetting the timing spot-on using the oil pressure light as a test light.

David