SuzukiSavage.com - Print Page

SuzukiSavage.com
/cgi-bin/YaBB.pl
General Category >> Rubber Side Down! >> Carb Leak Diagnosis Pt. 3
/cgi-bin/YaBB.pl?num=1195508074

Message started by vroom1776 on 11/19/07 at 13:34:34

Title: Carb Leak Diagnosis Pt. 3
Post by vroom1776 on 11/19/07 at 13:34:34

part 1 (http://suzukisavage.com/cgi-bin/YaBB.pl?board=RubberSideDown;action=display;num=1176142433;start=)

part 2 (http://suzukisavage.com/cgi-bin/YaBB.pl?board=RubberSideDown;action=display;num=1180531519)

Hello all!

should've been called carb ovefrflow diagnosis...

reminder: not for the stock carb, for a mikuni VM 38.

anyway, I tried adjusting the float from 20 mm to 16mm... still overflowed.

Finally tried removing the vacuum line, and capping the vacuum ports on the carb and petcock with 3/16" (I think that was the size) vacuum caps. Seems to have worked. No more overflows in several hundred miles. Rough/eratic idle, need to readjust the float height and get the pilot circuit dialed in.

So, anyone having a similar problem and the needle valve is working, you might try my solution.

Best to all and Happy Thanksgiving!

V

Title: Re: Carb Leak Diagnosis Pt. 3
Post by smokin_blue on 11/20/07 at 03:03:50

Time out.......... ???

What vacuum ports on the carb? I am pretty sure the VM carbs don't have vacuum ports. The only vacuum port you would have with a VM carb would be if you installed a new manifold with one to drive the petcock.

Can you show a picture of the ports? or describe them in detail where they are?

Title: Re: Carb Leak Diagnosis Pt. 3
Post by Savage_Rob on 11/20/07 at 06:10:03

He may have added a vacuum port to the carb, as I did to my Amal Mk2, to allow for normal functionality of the LS650s petc0ck.

Title: Re: Carb Leak Diagnosis Pt. 3
Post by Savage_Greg on 11/20/07 at 07:16:43

Don't they have synchronizer ports???

Those are vacuum.

Title: Re: Carb Leak Diagnosis Pt. 3
Post by smokin_blue on 11/20/07 at 18:35:57

Savage_Greg wrote:

Don't they have synchronizer ports???

Those are vacuum.

Not on the VM's that I am aware of.

Title: Re: Carb Leak Diagnosis Pt. 3
Post by vroom1776 on 11/21/07 at 11:13:23

there's a port on there on the one I got from Lancer. it goes through the throttle body on the engine side of the carb. I had it hooked up to the vacuum port on the petcock for the same reason as Rob. Will take a pic as time permits.

V

Title: Re: Carb Leak Diagnosis Pt. 3
Post by vroom1776 on 11/26/07 at 13:21:54

Pic time!

you can see the vac port in both pics... on the left hand, upper, & engine side of the carb. It goes all the way through the throttle body.

http://i55.photobucket.com/albums/g152/vroom1776/PICT0111-1.jpg

http://i55.photobucket.com/albums/g152/vroom1776/PICT0114.jpg

btw: the slide & needle are obviously out for these pics.

btw2: set the float height back to 20mm... erratic idle is NOT fixed... yet.

V

Title: Re: Carb Leak Diagnosis Pt. 3
Post by smokin_blue on 11/27/07 at 20:01:49

I agree it is a vacuum port although not stock for a standard replacement VM36 carb. It has either been added or it is a non standard carb from some other application. Either way it will provide vacuum for the petcock. however if you are having idle problems (different from your overflow) it could be a vacuum leak causing a lean condition at idle. This could be either the vacuum hose being cracked, the vacuum port leaking where it goes into the carb body, or the rubber intake boot on the engine being cracked or leaking where it mounts to the engine. .... or it could be something other than a leak. Normally if it is an air leak it will run better on just a little bit of choke....that is a sure sign of a lean condition.

you said it overflowed gas but the valve needle shut off. Did you shake the float to listen for gas in it? (first question is it the old brass style?) I had one on my old GT spring a leak and sink a float. valve worked fine but the float wouldn't float!!

Title: Re: Carb Leak Diagnosis Pt. 3
Post by vroom1776 on 11/28/07 at 11:42:57

Hey blue...

all problems seem to presently be fixed... the idle problem turned out to be corosion between the spark plug wire and the spark plug cap.

as to the floats, they are the plastic ones. I checked their bouyancy many times... I think there was no vacuum or airt leaks, but the vacuum was pulling too much fuel into the bowl. It was kind of odd because it only happened occasionally. I'm only running on prime now with both vac. ports capped. Seems to have solved the problem. Once I'm sure, I'll do the petcock mod.

BTW, VM 38