Suzuki 2 Strokes

All,

After trying for over a year+ to try and get my stock carbs to tune I gave up and bought a pair of 34mm VM's set up for 2 Strokes from "bikebuzzard" on eBay. Below is the details of the carb as shipped.

"A NEW 34mm Round Slide Mikuni carb used on all kits of bikes and ATV's!.. ( usually older 250's and 125cc models ).....this carb comes with the following jetting:"
#260 Main Jet
#35 Pilot Jet
#159 Q-2 Needle Jet
#6DH4 needle
#2.5 Slide

My bike has int/ex port and polish, gasket match, Jemco Street pipes, and Uni Pod filters. From all that I have read on here, a 120 main is a good starting point and the rest of the jetting I'm assuming is good to go since the carbs are set up for a 2 stroke. Maybe a bit of needle adjustment? Will my stock needle/needle jet be a good swap or due to the additional air volume of the 34mm and the larger 2.5 slide on the new carb is this out of the question? I'm excited to get my project finally road worthy after 2.5 years of work after starting with a "barn find".

Any recommendations and help is greatly appreciated.

Thanks,

Marion

All,

Well the project did not get a good start today. Looks like the new mikuni's have a 40mm outlet and the 69 T700 carbs have 42.6mm outlet? The new "Mikuni" has a thinner outlet also and the groove to fit in the intake is also further back on the outlet flange. I used the stock clamp tightened all the way down and the carb pulled right out.

Is this the norm and if so what can be done? Besides return the 2 carbs?

Thanks.

Marion

For the engine side of the carburetor, are you using 1.the composite intake manifolds (mostly rubber with a metal flange incorporated into the intake) or 2. the aluminum flange with a rubber connector. You may need to switch to the second type of intake and search Sudco for a rubber intake connector that will work with the new carbs.

http://www.sudco.com/Carburetor01.html

For the air cleaner side, are you going to try to keep the air cleaner assembly or switch to individual filters? Uni foam filters would work well although you will need to make some sort of support brace for the carbs. If you are going to try to keep the air cleaner, you might need a later version and again you may need to play around with the mounting points.

diamondj wrote:For the engine side of the carburetor, are you using 1.the composite intake manifolds (mostly rubber with a metal flange incorporated into the intake) or 2. the aluminum flange with a rubber connector. You may need to switch to the second type of intake and search Sudco for a rubber intake connector that will work with the new carbs. .

If you switch from the old (composite) intake to the later model (2 piece) intake, there is a significant length difference between the two. Newer model frames have air box mounting positions for both styles. early frames (such as my '71) only have mounting points to accommodate the early, 1 piece composite intakes.

Well I got the carbs mounted and the bike running on the new 34mm mikuni's.

I took off the stock clamps and used some stainless hose clamps. I pushed in the carbs to a stop and clamped them down. I'll see how long that holds up. I have new intakes boots on the engine and I really had to push to get the stock carbs installed. With the new 34mm's I have a an extra .062 on each side of the carb to get compressed and seated. It looks ok and is sealed 360 deg. The stock clamps were limited and just could not really take up any slack.

After a couple of adjustments to the cables, idle and the pilot mixture screws, she fired on the 2nd kick! Drove it around for 15 minutes in the neighborhood. It did pretty well for out of the box. The engine low end is good but the midrange has a bit of uncertainity/blurble to 4.5k but then it pulled nice really up to 7k. So looks like I'm in the ballpark. My first urge guess that I should move the jet needle down? Or just go with a better overall needle/jet combo? Can someone recommend a setup. I have seen the P5 159 jet come in some other Mikuni 34mm's with various needles.

I picked up this bike 2.5 years ago and had not worked on an old school 2 Stroke for 25 years so I'm trying to get the bike finally ironed out!

With the Q2-159 jet can I use the stock needle? Mine looks to be in good condition.

i found some intakes that worked w/ the 34's.ebay? my stock ones wouldnt work.i believe i used the stock (32mm needles) but did go w/ a 3rd needle jet (not the stock or the 34mm one) needle circlip on 2nd from top pos. (lean)i used 115 mains- even thou the plugs looked good i had a seizure after race 2. put in 125's and it seemed as good. so just to be safe i went w/ 140's. ill know in april or may when i get back to the track. i had the same good luck w/ start up after changing carbs. 2-3 kicks.[URL=http://s1253.photobucket.com/user/ ... .jpg[/img][/url]

So I decided to move the needle down. When I took out the needle I saw the clip as already in position 2. So I moved it up to the #1. The bike ran great up to 5 k or so and then it labored a bit to accelerate and I had to let out of it as I was in the neighborhood So I will drop it down to the 3rd nest time to get the feel for that position before I start buying a different needle/jet combo or at least another needle.

Anyone willing to share their setup?

Does this site have a "Sticky" section where people can post How To's for technical info in particular?

Thanks,

Marion

That would be nice to have in this list category and a sub folder for each engine size

mario03srt wrote: Anyone willing to share their setup?

When I ran VM34's on my race TR500 I used 159-Q0 needle jet and 6DP4 needle. This gave the crispest response thru the entire rev range.

We usually have to go to P-6's on the H2's. The needle works fine.

This is the setup that Jim Lomas uses.
http://www.jl-exhausts.com/mikuni-vm34- ... -550-p.asp" onclick="window.open(this.href);return false;

I sincerely doubt that's what Jim uses, he just buys in and sells or just has drop shipped. his seeley rep frames are what we used to supply him until he started telling people he made them ........... supply then ceased.

we will probably be making seeley rep frames again something in 2015 and spondon rep Suzuki frames

All,

I put in the stock 32mm needles and while it ran ok on the 3rd position the top end was not there over 5500 and the plugs looked very rich after a 1/4 mile chop at 4k or so. I could drop the stock needle it a notch but I have a pair of 6F4 needles that are on the way from DCC that they recommended. If that does not pan out I will definitely go to a smaller Q0 Needle Jet like desmocat has indicated in his reply, as this one is probably too fat being a Q2.

Thanks for the replies!

Marion

Cincy, Ohio

Which needles are in there at the moment? 5F16, 5FP8, 5FP17 or something else? 6F4 was stock on a Yamaha TD2

The thing about needles and needle jets is that needle jet changes have the most effect at small to mid throttle where even a small change in diameter represents a large percentage change.

With needles there are different root diameters and different tapers (angle and where it starts).

That's why it's important to know what throttle position is the issue and exactly what needles are in there.

The simple way to work it out is to mark the throttle at 1/4, 1/2, 3/4 and see where the jetting is good or bad and then work from there. the engine speed is less important than throttle position

I have fairly extensive lists of needles here and of course Ivan has done a lot of real world testing and has developed needle profiles and needle jets for particular bikes.