1978 CB400T VM32's

C

Cooter1979

New Member
Hey guys looking for some help/suggestions in which direction to go with jetting my VM32's from Dim City Cycles.
History, I rebuilt the bike last year new ring gaskets re-seated the valves and had the stock carbs rebuilt. I also added a MAC 2 into one exaust. I spent all last summer fighting with leaky, flooding, all around crapy carbs.
So this spring I got 2 new VM32's but I'm running way to rich I've gone from the 185 main 35 pilot to 170 main 25 pilot set the needle to the leaneast postion. The top end 1/8 throttle and above is better still a little rich but the low end is a mess kinda floods out and stalls.
If I shut off the fuel or pinch the line the bike leans out and the idle jumps from 2000 rpm to 3500-4000. I've tried backing the air screw out past 3 turns it gets better but still to rich.
Do I go to a smaller pilot or can I change the air jet? Should I be changing the needle jet and jet needle?
I'm hopeing some one on here has put these carbs on a CB400T before.
Thanks in advance for any help.
 
32 is probably a little large but that's what you have.... 25 slow jet "should" be small enough, so something else is getting in teh way. Check float level for a start and make sure that the "choke" (enricher) plunger is sitting fully closed.

What Needle and needle jet did they come with?
 
There is no timing adjust other than lineing up the timing marks, the rest is done by the CDI. The compression cold is 155 and 158psi. I'll get a warm compession later need to go get some gas.

The carbs came with 6DH7 Jet Needle, 159 P-5 Needle Jet, 2.0 Air Jet.

Choke plunger down is off correct?
 
make sure you have the air corrector jet (6 oclock position inlet side) removed or it will run way to rich

i would try a 30 pilot and about a 140 main needle all the way down and then tune from there

also run a 3.0 slide
 
was planning to replace the stock 32mmCV carbs with 26mm VM carbs. will that do the job or is it a step back.

more importantly, I would like you to have a look at my post here>> http://www.dotheton.com/forum/index.php?topic=48481.0 to help me decide on getting one of these bikes or not.
cheers from India
 
if you can get them bored to 28mm they will work awesome

as 26mm they will be decent
 
Thanks Cxman. I final got the chance to work on the bike, removing the air correctors made a huge difference. I'm very close to having it tuned now. Still waiting for new main jets to come in. But the bike will idle now and might be a bit lean side, going back up a jet size to 30 pilot like you suggested.

Thanks Again
 
awesome glad to help

dont change to much at once mikunis need to be jetted from the bottom up

swap the pilot to the 30 and give it a try then try raising the needle a groove at a time

if it is still lean at top end set the needle back down and go up a main jet size and repeat

till you get it how you like

i would pull the resistors out of the spark plug caps and replace them with a brass rod

and then change to iridium plugs it will run a lot better with them
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light

    • Spread the Love

    Back
    Top Bottom