If anyone has a caliper to measure the diameter of the bolts (the threads), the thickness of and diameter of the hole in the sprocket, the info would be usefull. Something as simple as a specialty bolt would solve the problem. In fact, I'll bet the bolt already has a space near the head where the OD of the bolt is the same as the OD If there is a big enough of the difference between the bolt and hole size, a custom flanged steel washer would do the trick too.

Not an excuse for the problem to be corrected in China, but maybe a cheap solution to retrofit?

Of course, if jetmoto changes the sprocket, as opposed to the bolt and thread, a rear sprocket could fix us up, and be cheaper (time is money) that coming up with a custom solution. How many bolts are in the rear sprocket? I can't tell from the pictures on jetmotousa.com, but it looks to be 6. If it is, rotating it 20 degrees and redrilling smaller holes wouldn't be a good idea. If it is a 4 bolt sprocket, it could probably work, but that kind of work would require a press and a lot of patience.

-JNY

EDIT: just saw your post. Wow! I thought I was getting creative! Glad to know it was that easy. Great job. The bolts go in from the left side, through the sprocket, and into the hub, correct? You have lock washers where exactly? I got lost at that part.

RE-EDIT: Oh, locknuts, not lock washers. doh! Well kick ***! If anyone hasn't cut a bolt before, put a nut on it and screw it down past where you are going to cut and then cut / grind the bolt. Then screw off the nut and throw the nut away. It will typically mess up the threads on the nut while it straightens the threads on the bolt, and it definately makes it easier to get the bolt the thread into what you don't want to strip. If you grind down a bolt while it's in something (IE, the hub) you can sometimes tear up the thread on the hub. Maybe not depending on the metals involved. Great info man! Keep it coming!

 

There are 4 bolts holding the sprocket on the hub. I reworked the assembly at work yesterday, and assembled it back together then.

It wasn't until I got home with it that I found that the bolt heads would rub slightly on the swingarm/bearing area. As I said I just ground down the bolt heads slightly and that gave me the clearance I needed. I know grinding the bolt heads isn't the most "professional" thing to do but hey... it was that or chuck it up in a lathe and have them turn the heads down. I didn't want to have to use button head bolts since you cannot get an allen wrench into the bolt head because it is right up against the swingarm if they ever needed tightening.

BTW, I used grade 8 3/8-16 bolts.

 

Oh! You ground the head, not the thread. I need to get mine so I can actually contribute to the discussion. I'm lost as to how it looks, so I'll shutup for now. haha

Sounds like you did a great job. I'm looking forward to getting mine. It looks like May 12-15 is primetime for delivery. It's coming from California to South Carolina, so I'm not sure what carrier will have it or if they deliver on weekends. Probably not, but who knows. I guess I will know more on the 7-8 when they ship mine out! =)

-JNY

 

The JetMotos have their little problems/quirks but they are a blast to ride, and well worth the price. The excellent service from Raceway ATV helps too! My son and I are looking forward to going out to an offroad park Saturday.

Hope it gets to you ASAP!

 

I had another fun outing today on the 250, my Dad rode his Honda 300 Fourtrax (2wheel Shaft drive). I hate to say but his 300 kicked my butt! His had so much more climbing power, my Jet 250 would be bauging down in 1st and his Honda would be doing fine in 2nd up the same hill! The Jetmoto 250 is fun but it does not have the power needed to compete with a Honda. I know the Honda was a 300 but the power was way more then 50 or so cc. I still had fun on the Jetmoto and we climbed some insane mountains hills shown on the new video. The mountain you see us coming down we had just climbed. The Jetmoto managed to do it but it pushed it to the max and then some. If the Motor was going to give out this would have been the murder weapon. As long as I kept the quad moving it managed to power up the hill. It did power out at a real steep spot but I managed to rev and feather the clutch and got it going up again!
As you can hear the first hill in the vid the Jetmoto pretty much powered out at the top but none the less made it up.
Day out with my Dad

 

WOW! Great video man! How tall/heavy is your dad? The 250 seemed to have more than enough power slinging you around! Haha! The last part of that video was awsome. The wheelie off the top of the lip is the only trick I can do, but I love it! I did see what people are saying about the suspension being very soft. This is definately not a jump machine if you are over 200lbs I would think. I'm really going to have to do something to tighten the suspension, but the climbing was great. That is just with a 14 tooth and jets? Man! I want to see what it would do with the gears dropped even more (bigger rear gear.)

I'm even more pumped now, gonna watch your video again!
-JNY

 

pimpsmurf, careful on the vid your going to wear it out so no one else can see it![img]i/expressions/face-icon-small-wink.gif[/img]
I really would hate to gear it down any lower, I hate to lose the top end! But for climbing it could use loose a couple more teeth, but it will climb it just powers out. It's fine for trail riding and over all riding stuff as you can see! I am happy with it, just wish it had some more HP, thats where I think it's lacking!
BTW my dad is around 190ish and 5'10" (16 year Heart Transplant survivor) but thats me on the Jetmoto in all shots! My dad did ride the jet for a few min. and he liked it but it's far from the comfy of the Honda.

 

You could always get a 2nd set of rear rims and some smaller tires for doing climbing. If you go down to a much smaller tire in the rear, climbing hard surfaces like that loose dirt/rock would be much easier, although sand would be a problem. haha

Ahh! I thought that was him doing the climbing at the beginning, and thinking he was taller, figured he weighted more as well. I, being heavy, am trying to get a grasp on how it will handle with me on it. I guess I'm just going to have to try to diet harder.

UPDATE! Been dieting for weeks because I had to do math when using my scale (it passed 270, and went back around to 30...) I just went into the bathroom and weighted myself because someone mentioned that it looked like I was losing weight today. I have lost 30 lbs in 3 weeks! I'm down to 270 with clothes and shoes on! Maybe I wont' be too much of a fatty for the 14 tooth gearing afterall! HAHA

As far as improving horsepower goes, after the 6 month warantee is done, I plan to break the whole thing down and rebuild it. I have a guy that does custom work on cars (bored his truck engine out to the point that you can't drive it in the rain, ever.) He will help me port and polish the intake (his specialty with go carts, trucks, cars, etc), and then we can play with jets and maybe even an aftermarket ignition. If we could get a bigger spark with more air/fuel and tuned timing, this bugger could put out a bit more power I think. What is great about aftermarket ignitions, is you can get them with buttons where you can have one button for slightly advanced timings (for climbing) and another for higher timings (for flats and top end.) With the right jets and more air, it could happen, but I don't want to experiment until I'm sure it's stable enough to do so with. I think there is some changes that could be made to the piston as well to provide better vaporization, although that kind of physics is out of my field.

Watched your video again, and this thing is going to rule with spacers. I don't think I ever got a responce about spacers. Anyone know what, if any, modification is required to allow full steering? I just can't see anything that would get in the way. I plan on doing spacers and maybe alluminum rims if I can get some cheap.

-JNY

 

Great video!! I think raceway sells alluminum rims for the jetmoto...

 

Watching that video, proves to me what you yourself said.
"just wish it had some more HP, thats where I think it's lacking!"
Years ago I had a Honda 200X three wheeler. I know it is hard to judge from a video, but that hill did not look that steep to me, yet it was kicking that Jetmotos ***. I believe my old 200X could tow the Jetmoto up that hill faster than the Jetmoto could climb it under its own power.
Modern Thumpers kick ***! Anyone who has ridden a Honda 450F will agree. The Chinese need to step it up and start to copy a more modern engine. If they had a copy of a modern liquid cooled 250 engine in that quad, it would rip up that hill.
I think a person is better off buying a used Jap. unit, just my opinion. I bought a Kazuma 90 for my kids and it has proven to be a good little quad for the kids to tool around on. I have had to work on it more than I feel I should have, but I really don't mind, because I did save a bunch of money on it. I do figure however that it will be hanging around for a while, since there is no resale value. I would rather keep it and let friends and family use it than basically give it away once my kids are done with it.
Sorry for the long rambling. My point is that the Chinese need to improve quite a bit before I would consider one for an Adult rider.

Just my opinion.........
Shawn