I have swapped the carb on my Hawk as well, but I am having excessive idle issues when cold vs. when hot. If I tune the bike to idle properly while running hot it won't start while cold even with the choke on without giving it gas or having to readjust the idle air screw on the side. I have the standard recommendation jets 30/115 in the bike. I adjusted the fuel mixture screw in the front a bit and it has helped, but I noticed my rpm's take an excessively long time for them to drop. I'm betting I have an air leak, so I'm gonna pick up a bernzomatic to check for leaks, but if anyone has any other ideas why mine behaves so erratically, please let me know.

That screw in the front of the carb is an absolute son out of wedlock to adjust.

If you don't find an air leak, the problem is definitely caused by improper adjustment of the pilot mixture screw (PMS). Always adjust the PMS when the engine is hot, not warm, hot. ;)

Quote of the week! :D

I feel ya man, I am also having lingering idle issues. :grr:

I couldn't get my idle down enough on the 30 jet, and had to move to the 20 to get it even remotely close to being sane. Right now I have to warm it up for quite some time before it will idle on its own, otherwise it just dies. I think im still running rich maybe?

If anyone has recommendations for a bike that will easily choke start, but it need a good 10 minutes of riding before it will idle on its own, id love to hear it.

Also, my bike seems to perform better in the top end and punch when its colder, too rich on the main jet?

Thanks guys!

:thanks:

Have you checked your valves? tight valves will cause an impossible idle condition.
If your WOT (wide open throttle) is better when cold the main jet is too big.

When I had Hawks and Vipers (sold them all) I used OKO / KOSO. Just remember if you buy on Ebay a Mikuni, it will be a knock off and not a TRUE Mikuni, some work good and some are just junk and you will know junk when you have idle and performance problems. Also just keep the carb you have on it and fixit if you are having problems, you don't need a new carb. I can say that when we did carb replacement tests the guys had to hack/refab on the exhaust.

i dont have a hawk, but the storm 250 ... i have the 40/115 jets pms about 1 1/2 turns out ... starts with no choke every time, it idles fine but is a bit richor so it would seem from the black soot on my plate holder, but i still need a better air filter and exhaust, so rich is ok for now and ill see what it does after those two upgrades (was going to do them this week, but going to pick up my 1980 gs850g and get it on the road again)

Yeah, I couldn't find them either. I ordered the one in the link thinking it was the idle screw but apparently it's the mixture screw. Any one know where to get the idle thumb screw for the Mikuni VM26?

What is the best method for removing the tamper proof screws? I saw Motocheez uses a dremel and slots it, but I also found this video https://www.youtube.com/watch?v=0DPcR-dvT50

What did you guys do?

Depending on how the carb is sealed, I either use a Dremel Tool Cutoff Wheel, or a Saw Blade to cut a line and remove with a flat head screwdriver.

Or if the tamper proof screw is "recessed" into the carb... I will bring out my "Alden Grabit/Micro Grabit Pro Extractors"

https://www.amazon.com/Alden-8440P-G.../dp/B001A4CWHO

https://www.amazon.com/Alden-4507P-G.../dp/B000Q60UOO

Alden tools can be found locally at 'Home Improvement' (Lowes, Home Depot, Menards, etc.) type stores for much less than Amazon usually has them for... but Amazon has all the reviews to read :D

Can't you just cut the heads right off? After the bowl is out of the way, the remaining screw studs could be removed with a pair of pliers. New stainless socket head cap screws would be much easier moving forward.

I used a center punch and tapped them out.

The heads are recessed so you can't cut them off.

Dat ist ein bummer.

i used a dremel with a 1.5" cutoff wheel, sunk it down right into the alluminum and the brass of the skrew heads untill there was enough of a slot for a regular skrew driver. put it back together with phillips head skrews, and the cuts into the alluminum around the bolts makes no difference, that is only there to make it more difficult to get ahold of the skrew heads with pliers or the like.

ultimatly after cleaning out the idle jet and getting it to run ok, i replaced it with a mikuni, its really a crap part. i suspect terrible atomization of the fuel.

the mikuni vm28 i used was only $30 new on ebay. and a set of jets was like $10 with the vm28 and a 110 main jet it runs perfectly.

i wouldnt worry about ruining that carb, throwing it away is a good option.