Kawi2strokes.com Forum

Ive got a '71 H1 project going that is close to getting kicked over for the first time. I swapped the stock round slides for some Mikuni VM28mm flat slides. I was looking for some advice on some starting carb settings (ie. jet sizes, atomizer, and needle settings) to make it easier on tuning. The bike has had the squish on the heads have been reprofiled and I got a set of custom expansion champers made for it.

What are in them now?

_________________
Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

They are brand new carbs. They came with 4 stroke atomizer so I gotta buy 2 stroke ones.

I haven't worked with carbs that small. The book has very small jets from Mikuni, so I hope someone else can help......

_________________
Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

Are you sure you can get primary type needle jet (NJ) for this carb?
Although there are some indications that primary type 169 series can be used instead of the bleed type 175 series in this carb.

The "Bleed = 4-stroke and Primary = 2-stroke" is not always true. Several OEM two stroke carbs are fitted with bleed type NJs like Yamaha RDs and Suzuki RGV250.

I would try the carbs as they come (assuming it is VM28-418). There's a good chance it is rich all over, but don't give it a hard time before you know it's NOT TOO LEAN. For extra safety you could start off with a #200 main jet instead of the #180.

If you decide to convert to primary type NJs then you may have to change everything else.
-Bleed type carbs typically have smaller pilot jets.
-Bleed type carbs typically have smaller cut-away slides (only #2.5 exists for this carb).
-Air jet (AJ) is important on bleed type carbs. Primary type carbs often don't have AJ fitted.
-Bleed type and primary type carbs typically need different needles.

Here's my guess for a conversion to primary type (and it might not even be close):
Needle jet: 169 series P-2 (assuming it will fit the carb)
Needle: 5FL7 (start in middle)
Main jet: #200
Pilot jet: #30
Air jet: Remove

And be careful....

PK

I ran 30mm flat slides on my H1 that I owned a few years ago. They where aftermarket carbs from Japan (OKO) and came with very short emulsion tubes. After lots of research I found that a Kawasaki KX85 or 100 had primary tubes that would work. You could see the difference with a flashlight when you whacked the throttle. With the taller emulsion tubes jetting was easy and ounce sorted they worked great. I wish I still had the jetting numbers written down but they went with the bike when it was sold.
KX85 tube is on the left, carbs came with the short ones on the right and didn't work with a 2-stroke