Tuning and jetting hawk 250

[redneck51587]

Ok so first let me begin by saying I'm sorry for this question that has probably been asked a million times, but I'm trying to figure this out. I bought the mikuni carb on Amazon and a pack of jets. I live in Indiana at approximately 800ft above sea level. I have a stock exhaust and have done the air box mod. Can someone tell me how to tune my carb and what jet to install to start with????? My hawk runs great until 3/4 throttle then it really bogs down. I'm sick of it running like crap and can't wait any longer to get the new carb on.

[Megadan]

Jetting recommendations with an airbox mod and stock exhaust on the Mikuni clone at your altitude.

Main Jet, 110
Pilot jet 25 (recommend also buying a 27.5)
Needle set at 4th notch from the top/1 down from center.
Idle mixture, start 1 1/2 turns out from lightly seated.

This will get you very close, but obviously fine tunibg may be needed to get your bike ideally jetted.

[redneck51587]

What pilot jet typically comes stock with the mikuni?

[imapdog]

Originally Posted by redneck51587

What pilot jet typically comes stock with the mikuni?

both my vm26 came with 20 pilot

[blanc12]

when I got my Mikuni I put in a 110. I got the wrong pilot jet so I left it stock. Just put in a 25 and now the bike runs great.

I am at 400 feet. running a 110 and a 25. everything else stock. Mixture screw out 1 1/2 turns.

[Megadan]

Originally Posted by redneck51587

What pilot jet typically comes stock with the mikuni?

THe Mikuni comes with a 100 main and 20 pilot (as imapdog stated).

If you want to order genuine jets, which I highly recommend, then your part numbers are;

Main: N100.604 - https://www.jetsrus.com/a_jets_by_ca...arge_round.htm

Pilot: VM28/486 - https://www.jetsrus.com/a_jets_by_ca...-486_pilot.htm

[redneck51587]

Thanks guys I really appreciate it. I ordered the pilot jets yesterday from rocky mountain atv 2 day shipping. Fingers crossed that they get here so I can get this thing fixed up saturday morning.

[Jeff Richardson]

Yeah I ordered a bunch of jets from Rocky and got the mikuni carb today. Drilled the stock jet somewhere between 105 and 110, shimmed the needle 3 washers and have some mid throttle bogging. Funny enough around 50mph I can go full throttle and really get a good pull. Spark plug sooty. Wondering if it's valve lash?

[Jeff Richardson]

Not to hijack thread just seems like good place. :-)

[Megadan]

Originally Posted by Jeff Richardson

Yeah I ordered a bunch of jets from Rocky and got the mikuni carb today. Drilled the stock jet somewhere between 105 and 110, shimmed the needle 3 washers and have some mid throttle bogging. Funny enough around 50mph I can go full throttle and really get a good pull. Spark plug sooty. Wondering if it's valve lash?

Why are you shimming the needle? Put the clip in the 4th notch down from the top and remove the shims.

[Jeff Richardson]

Oops, I worded badly. Shimmed the stock carb and mikuni came after. I had already ordered the mikuni and jets I was just doing trial and error on the stock carb. Also, the bike has eBay exhaust and it's changing colors. Airbox also modified with cutout. I love the bike. Just a few minor tuning issues. My test run was a 20 mile trip to BMV so I could register. 1-2-3 shifts from stop are tricky because of bogging issues.

[Megadan]

Originally Posted by Jeff Richardson

Oops, I worded badly. Shimmed the stock carb and mikuni came after. I had already ordered the mikuni and jets I was just doing trial and error on the stock carb. Also, the bike has eBay exhaust and it's changing colors. Airbox also modified with cutout. I love the bike. Just a few minor tuning issues. My test run was a 20 mile trip to BMV so I could register. 1-2-3 shifts from stop are tricky because of bogging issues.

The ebay exhaust will change colors no matter what you do.

I would suggest maybe stepping up to a 115 main jet with that exhaust installed, especially if you have an intake modification of some kind.

What size pilot jet are you running?

[Jeff Richardson]

OK so jets came in today I'll switch to new carb and try 25 and 115. I have jets to go smaller/bigger by 2.5 or more. Mixture screw should be one and a half turn? And to answer your question I hadnt tried drilling the original pilot jet just did the main.

[Ariel Red Hunter]

Originally Posted by Jeff Richardson

OK so jets came in today I'll switch to new carb and try 25 and 115. I have jets to go smaller/bigger by 2.5 or more. Mixture screw should be one and a half turn? And to answer your question I hadnt tried drilling the original pilot jet just did the main.

Yes, that should put you in the ball park. The way I do this is to set the needle in the middle groove, and the idle mixture screw at 1 1/2 turns out from lightly seated. Then I change pilot jets until I get a strong 1250 to 1400 rpm idle. By strong I mean that the machine can pull itself along on level ground with no action on the part of the rider in second gear, once you've gotten it moving with clutch and not more than 1/8th throttle. Once you've gotten this far, then crack the throttle to 1/8th again in second gear and you get instantanious acceleration up to where the engine wants more throttle, open it up to 1/4 throttle. You are looking for immediate response. You have now reached the upper limit of pilot jet range. Next, with the engine well warmed up, check main jet performance...ARH

[Jeff Richardson]

Good stuff MD and ARH!!!
Mikuni came with the needle clip at 3rd slot so I left it. 115 main and 25 pilot. Ran great but can't say I have a strong idle though. 1,500rpm is close to dying. I set little below 2,000. Top end felt good managed 58mph @8,000rpm or so. I'm heavy rider at 260lbs. Should I go up a size on both pilot and main? Or do anything with needle clip? Thanks!