And so my Hawk 250 experience begins.
 

https://scontent-sea1-1.xx.fbcdn.net...3a&oe=5A319592

Got the crate this morning unharmed. Now time for new fluids, sparkplug, VM26 carburator and/or jets, JT sprockets and chain.:yay:

Congrats! Hope you love it. Thanks for posting.

Nice! Depending on your altitude on the Mikuni, start with a 25 pilot, 105 main, and needle 1 clip down from the center.

Take your time and check everything very carefully. People talk about brake calipers and sprockets falling off. Mine came with 3 tight bolts and one finger loose bolt. I haven't changed the stock chain or carb (yet), but my chain came piano string tight, had to loosen that way, way up. Check the wire runs, even if they're zip-tied in place. Nothing has any lube on it. When you think you're done, go back and check everything again. I got way too excited about going for my first ride.

It might be better just to dis-assemble the whole bike and start over. :hmm:

CARB Approved
 

I only wish the Hawk 250 was street legal in California. :hmm: :cry:

That is exactly what I did with mine. Down to motor and frame. That is how I discovered the loose sprocket situation.

Dan, I'm sure that's also how you corrected wiring issues before they became trouble.

Dan, I'm at 3300 feet here in Montana. I bought the 10 jet kit for the VM26 Mikuni. Carb (new one) goes on tonight, so far I've blue loctited every shock, wheel nut, on the tripple clamp. New oil and NGK Irdium spark plug put in. Replaced front fork oil with Yamalube 15w. Going to finish it up tonight with new japanese made 428 chain and JT sprokets 17 and 44, need to get more blue locktite and black zip ties to clean up electric wiring and cables.

Where did you get it from, and what was your cost (if you don't mind me asking)? Also did the MCO state "motorcycle" or "dirt bike"?

That would be correct sir. I wouldn't really call them issues, but I definitely wasn't a fan of how some of the wiring was routed, so I put them to "Dan spec"

Sounds like you are doing what I did with mine, mods right out of the box.

Being at 3300ft on a stock bike, a 105 or maybe even a 102.5 main jet might be the ticket. The 102.5 won't come in the kit, but if you decide to delve into fine tuning the carb you can order a genuine Mikuni jet through Jetsrus.com. I highly recommend genuine jets. I bought the same jet kit you did and had nothing but issues trying to get my bike dialed in, and had inconsistent threads as well as one jet that was blocked with debris.

As far as the pilot jet, the 20 size that comes in the VM26 clones should work ok for you at that elevation, but will still likely be a little lean. A 22.5 or 25 would be just about perfect for your elevation. You are roughly 2500ft higher than I am and I have found a 27.5 to be the right size on my modified bike, with the 25 being a hair lean. The general rule of thumb with Mikuni jetting is a half a jet size for every 2500ft change or 25 degree difference in temp. Since nobody wants to re-jet all the time for temperature changes, we primarily focus on elevation lol. My method for temp changes has always been to set the fueling up for cooler weather (50-60 derees), so when it gets hot the fueling will be a hair richer and help the motor run cooler.

Needle position on the Mikuni tends to be center or 1 slot down from center/4th slot down from the top.

I really do suggest some "half step" jets if you really want to get that carb dialed in. Taking the time to really dial in the carburetor will give you the best of both worlds. The best performance AND fuel economy. I still average mid 60mpg with mixed riding and a heavy hand.
Mikuni Jet numbers for the clone carburetor.
Main: N100.604 - https://jetsrus.com/a_jets_by_carbur...arge_round.htm
Pilot: VM28/486 - https://jetsrus.com/a_jets_by_carbur...-486_pilot.htm

Last little point to touch on that you will likely run into with the 17/44 gearing and an otherwise stock bike is that your top speed will never change, but your bikes cruise speed at half throttle will be higher. My 17/43 sprockets on a stock bike had a part throttle cruise speed around 50-55mph. It could do this all day long without ever breaking a sweat, but would have to be pegged wide open to do 60, and 62 was the fastest the bike would ever muster. Once I did the exhaust and intake and got the carb tuned again, I can cruise 60 all day long, never needing beyond half to 3/4 throttle unless I hit a steeper hill. Top speed is around 66-67mph, and I have a current max of 71 going down slight a hill...which is scary on such a tall light bike with knobby tires.

Border411: I haven't gotten the MCO from the distributor (Killer Motorsports) yet. I paid 1295 shipped.

Dan, thanks for the pointers. I discovered that that jet kit didn't fit the VM26, so I just put it in stock until I've broken in the bike. It sure is a sweet little thing, I let it warm up and spun it around the block (6 miles) then changed the oil (1st batch of Rotella 15w40) and then changed it, it was pretty gross still after only 6 miles, let it cool down and did a 2nd run on 2nd oilchange. Got 33 miles in on 1st day :yay:

Meh, order a handful of genuine Mikuni jets in the meantime. You have a good idea of what sizes to get, so you won't have to buy the whole catalog lol. The original jetting in that carb should be ok for your altitude anyway, maybe just a hair on the lean side.

FWIW, I broke my bike in from day 1 with a jetted carburetor.

Killermotosports is where I got my Hawk from too. MCO took about 2 weeks to arrive from when I submitted the request.

Do the MCO's for the Hawk state "Motorcycle" or "Dirt bike"????

Dan, I also adjusted the valves before 1st start of the engine (which had no clearance whatsoever), I set them to 0.004 for intake and exhaust for brakein. It was a little noisy at 1st, but it quieted down after 2nd oilchange and 30 some miles......so I'll keep an eye on it.

I will definitely look into the jet sizes you mentioned and buy 2-3 extras just because. I REALLY like this little bike. Uni filter coming, and I have a feeling a full exhaust will be in place shortly even tho I like the soundlevel of the stock exhaust as mine will be used for hunting too.

Just to be safe, when you ask for the MCO, tell them it has to say "motorcycle"....ARH

MCO Stated Motorcycle, but when you submit the request on their website, in the notes on the form I also put in "Please make sure MCO states "Motorcycle" as the vehicle type." Just to be safe.

I adjusted mine before the first start too. The real difference was, mine never really changed noise level. I gather from your previous reply that your first run was with the oil that came in the bike, then you changed it over to Rotella. That is the reason why your valves likely got quieter. The oil that comes in these things is total garbage, and I don't entirely think it's motor oil lol.

The exhaust makes a huge difference, so it is worth doing, but I can understand your wanting to keep it quieter. The standard ebay exhaust is a bit louder obviously, but there is always the option to run a slightly more expensive FMF or Pro Circuit exhaust system, or swap out the muffler that comes with the Ebay system for something that has a removable silencer. The other option would be to at least gut the cat from the stock exhaust, and at least clean up the weld on the inlet side of the header pipe.

I changed out the factory storage oil with Rotella 15W40 before 1st start, let it warm up and ran it slowly up and down carefully in throttle for 6 miles. Then changed it again with 2nd batch of Rotella 15W40.

Yeah, I will run it a little bit more before I decide upon complete exhaust work or not. I need to replace the chain and sprockets in the next two days. I just didn't have it in me after setting up the bike and locktiting everything to replace them quite yet. I spent a good 10 hours all together assembling things before 1st start.

Gotcha. Just make sure to keep an eye on those valve clearances during the first few hundred miles. They will likely shrink a bit and need re-adjusting one or two times. I just took the extra few minutes to check it at each oil change.

Taking that extra time to assemble it is worth it, but I can also understand not wanting to go back after doing it lol. I was the same way. After taking my bike apart a few times I am just about done with having to do so over and over again, but my OCD meticulous nature won't leave "good enough" alone, so I keep going back and working on it.

I ordered a 22.5 and a 25 pilot jet and a 102.5 and a 105 main jet based upon your advice. I runs fine except for a slight stumble at takeoff/low throttle. I now I will have some jet range and needle settings to play with to hone it in. I'm using this opportunity to learn more about carburation and air/fuel mixtures. I'm normally and FI guy. Thanks again, Dan.

While it's not an exact science, those jets should get you close. I always suggest starting with the richer of the jets. 25 pilot and 105 main, set the needle clip in the middle.

I am pretty confident the 25 pilot should work perfectly for you, but I always recommend having other sizes, because climate and other factors, even individual engines, can vary slightly.

The 105 main jet on the other hand may be a touch rich since it works well for people at sea level, which is why I suggested the 102.5. A plug chop will reveal where that sits.

Don't be afraid to ask any tuning questions on here. There are a few members on here that have a lot of experience with carb tuning besides me that can help guide and troubleshoot.

The only real thing to remember with these carbs is that, while each jet and setting mainly affects a given throttle position, I.E. The pilot jet primarily affects idle to 1/4 throttle, it still adds a tiny bit of fuel to both the needle range (1/4 to 3/4) and Main (3/4 to wide open). While half steps (22.5 to 25) usually won't affect the others enough to make a notable difference, a full step (25 to 30) can sometimes require tweaking of one of the other settings/sizes.

Great, now my gas tank is leaking in the seam close to the rear of it. Well, it is within 90 warranty so here it goes I suppose?

If you can get it fixed under warranty, definitely go that route. Why shell out money you don't have to?

I got some JB Weld Stilstik putty and smoooshed in on there. I'm gonna give it 24 hours before I assemble and see if it works.

I found this potential problem with my Hawk as well. Here is my solution from the previous post:
------------------
Additional vibration/noise isolation has been added to the tank area.
At the place shown on the following picture the tank was simply laying on the frame touching it with its welded joint, because the original rubber mount is too thin. There is a good chance that the welding on the tank would be damaged within the time due to the rubbing vibration of the metal to metal at the touch point. That could cause a gas leak, not to mention that the tank body works as a noise acoustic resonator. It was fixed by installing 1/4 inch thick rubber insertion as shown.

http://i1338.photobucket.com/albums/...psawpy545z.jpg

http://i1338.photobucket.com/albums/...pszepokfco.jpg

Some other tips to reduce vibration noise from the tank.

Rubber tube inserts on both sides:

http://i1338.photobucket.com/albums/...psomgtnlkb.jpg

Cover bracket installation changed.

http://i1338.photobucket.com/albums/...psiqyysqxu.jpg


Eliminating annoying vibration sound coming from gas tank when it close to reserve. Turns out, the source of the sound is the key hole cover. The fix is easy. Just make felt insert as shown. Make sure it is slightly smaller than the cower, so the cover's lip will hold it inside. The rubber wouldn't work. Because of higher friction, it would fall out every time you open the cover.

http://i1338.photobucket.com/albums/...psfpnayybi.jpg

Good to know about the gas tank issue! I'll get some more padding in there before it goes.

Here is a picture of the leak close to the petcock area.

https://scontent-sea1-1.xx.fbcdn.net...da&oe=5A23D8DD