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Posted by: mywifesquad
Welcome to the forum NJDale!
Thanks for the sprocket info.
Posted by: outofline
Yes thanks for the information, I'm sticking put with my gearing for now but this will come in handy for a lot of people I'm sure!!
Posted by: outofline
00XJ, any way you could make a short climbing video to see how the new set up handles climbing loads? Does it seem to have more ability then what you see in my videos? Like my last video of the first hill you can hear and see the 250 just barely making it up that hill! I had to stop filming on his first attempted because I was afraid I might have to grab his bumper if he stopped on the way up but he did make it every time as I did also on mine!
Posted by: outofline
The motor is a Yamaha clone but the rest is 100% Jetmoto or other Chinese parts manufacturers.
Posted by: 00XJ
Well I for one appreciate your hard work. Thanks!
BTW, I'm running 22" tires on the back of my son's 250 Sport. Going by his weight, he weighs 135#, you say the 46 tooth would be the one to get. Would the larger diameter rear tires affect which sprocket I should get?
Posted by: 00XJ
I went and bought one of the 50 tooth JT sprockets for my 250 Sport. It looks to be a high quality sprocket. I drilled out the smaller holes to 3/8" and so far have it and the hub back on the axle.
One thing I'm not too happy with is the hole for the hub is bigger diameter than the hub itself. I don't think it will be an issue, as I don't think the 250 has enough grunt to shear off 4 grade 8 3/8" bolts. I suppose you could have a machine shop make you a spacer ring if it becomes necessary. I'll keep an eye on it for awhile though. If your running the 14 tooth front sprocket you will be about 7-8 links short on the chain. The sprocket is pretty close to the swingarm toward the front end, again shouldn't be a problem though. This also might solve some of the chain slap on the swingarm because of the larger diameter sprocket. You will have to stack some flat washers between the swingarm and the sprocket/brake rotor guard to gain clearance.
I'm going to get the new chain this afternoon and put it on tonite or tomorrow, and try this setup out. I'll keep you all posted on the results.
Posted by: 00XJ
I got off of work early this evening so I put the new chain on. I didn't get an o-ring chain. They had to order the RK GXZ chain since they didn't have any in 130 link length. I bought a cheap chain so I could at least ride it to see how it ran. I will keep the cheap chain as a backup.
First, it made a world of difference. It now pulls like a 250cc thumper should IMO. I can lug it down in 4th and it pulls with no stumble, and it seems to have plenty of power up top too.
I had already drilled out the stock sprocket and hub to use 3/8"-16 bolts. I used grade 8 bolts, and had tapped the hub out to 3/8-16. I loctited the bolts in the hub, and then used lock nuts on the exposed thread sticking out of the hub. As I said, I don't think the quad has enough umph to shear off 4 of those bolts.
I have NO desire to beat the living crap out of it, or anything I own. Things cost too much money, and I have outgrown the need to beat stuff up for kicks. My son actually rides the 250, and we manage to have a blast without jumping, or pounding it to death. We mostly have trails in our area anyway.
As far as finding a Honda axle, I don't think I will put that much money/time/effort into the quad. It still will be a Chinese quad. So I'm happy with the thing now, and no more than we do with them I'll run it till it craps out. I am VERY anal about oil changes and maintaince. Heck it has maybe 40-50 hours on it and the oil has been changed 5 times! Other than breaking it in on 10w40 dino oil, it has had only Mobil 1 in it since.
Again, I appreciate your investigating the sprockets, and your input. I hope Jetmoto is reading this. They need to go with the 50 tooth sprocket from the factory.
Posted by: 00XJ
Originally posted by: outofline
00XJ, any way you could make a short climbing video to see how the new set up handles climbing loads? Does it seem to have more ability then what you see in my videos? Like my last video of the first hill you can hear and see the 250 just barely making it up that hill! I had to stop filming on his first attempted because I was afraid I might have to grab his bumper if he stopped on the way up but he did make it every time as I did also on mine!
Well I'll see what I can do about the video. Not real knowledgeable about that kinda stuff.
I went over to my "local" riding area and rode for about 10 minutes. I did climb a couple of hills with it. It felt like it was more "willing" to climb, and there was no bog when I opened the throttle up to climb them. I think I know what your saying about barely making it. We were out and climbing some L O N G sand hills and while it made it, it was about out of steam at the top. When we go back there I will have a better sense of how much of an improvement I have.
It seems much more "docile" to ride in the neighborhood now. I can putt around in high gear with none of the bucking and the associated chainslap on the swingarm as before. I hope all this makes some kind of sense. It just feels like a totally different quad now. Much easier to ride without worring about which gear your in.
Posted by: 00XJ
I'll agree with it was not quite right when I got it. I have gone to the 14 tooth front sprocket, the jet kit, and I am running 22" tires on the rear. The 50 tooth sprocket has made it into a much better "feeling" bike.
I have already drilled and tapped for grease zerks on all the rear shock linkage. I have also had to replace the swingarm needle bearings, and have added a zerk to it too. I crossed drilled the chain tensioner bolts, and added zerks to them also. I've disassembled the front swingarms, and cleaned and regreased them. I also have polished the intake. So I've been thru the thing pretty well.
The only real problem I see now are the crappy balljoints. I have put them in a press and pressed the bottom cap tighter to the ball stud. That helped, but I know it isn't a permanent fix. I would like to get a set from Moose Racing, but I have absolutley no idea where to start. I can't get any dimentions from them. I would have to buy some and see if they were the right one's. Talk about a crap shoot!
Posted by: 00XJ
Originally posted by: NJDale
I suggest to start by looking at 1980 to 1987 Honda equiptment - it seems like most of what they "copied" was from that era and make. If not Honda, then possibly Kowasaki or Yamaha from the same general era. Sometimes pictures from ebay of stuff people are "parting out" helps.
Thanks for the info. I just wish Jetmoto could get the Chinese company to say WHAT they copied so we could have a place to start looking, OR look into it themselves and sell the higher quality replacement parts. You've done the sprocket investigating, I did the rear brake pads, and swingarm bearings.
Funny you say Honda, I was told the engine is a Yamaha clone so I assumed the entire bike was a Yamaha clone.
Posted by: pimpsmurf
You don't need to do the DIAMETER*PI for the calculation. Just use diameter because if you multiply*Pi on both sides of an equation, it's the same percentage as not doing it at all.
So if you go from 20" rears to 25" rears, it's a 25% increase (either way) and if you like a 14/40 setup, then a 14/50 will compensate for rollout, but not any weight added because of bigger tires.
If you are looking for more climbing power, keeping the 20" with a 50 tooth will probably let us rev out 4th gear. What have you found with a 250ish lb rider?
Thanks for the top quality info man! I heard about this, and I'm glad it got posted!!
I wish we could get a line on some 3/8", grade 8 flat head bolts so we could countersink the sprockets.
-JNY
Posted by: pimpsmurf
If your hitting keys below what your aiming for consistently it may be a sign of CTS, but what is my excuse? lmao
-JNY
Posted by: oneOone
great info, thanks. how did you track these down, by luck or hours of searching?
heres a link for everyone else..
http://www.jtsprockets.com/52....l?&L=0&sel_uid=4551&p=
Posted by: NJDale
250 Gearing / Sprocket Answers & Information
250 replacement Rear Sprockets are available as part number JTR802-XX
The XX is the numer of Teeth. They are available as: 32, 34, 36, 37, 38, 39, 40, 42, 43, 44, 45, 46, 47, 48, 49, 50
They are for a 428 Chain; The current Jetmoto factury chain will fit (but you need extra links to make longer)
There are two sets of 4 holes, properly spaced. The small set are 8.5 mm and will fit the current allen head factory screws (NOT RECOMMENDED)
Tale the new sprocket to a machine shop and have them drill out the smaller holes with 3/8" bit. (VERY HARD material - you MUST have a drill press and MACHINIST grade drill bits)
Take the sprocket hub with you and have them drill it 21/64 ths and tap for 3/8ths National Fine (24 threads per inch)
Purchase (4) 3/8 ths x 1-1/2" Fine Thread GRADE 8 Bolts, (8) 3/8 ths Fine Thread GRADE 8 Nuts, and (4) 3/8 ths Stainless Steel Washers (Thin, to use as shims under bolt head - if neccessary, depending on gear selected, thickness, and length of shoulder at bolt head)
Grind off about 1/16" off bolt head to ensure clearance (depends upon exactly how far your bearings are set into the carrier from the factory)
IF gear is thinner than shoulder on bolts, you must use a thin washer UNDER bolt head to ensure tight fit against sprocket hub - if gear is as thick as bolt shoulder then dont use the washer.
Thread through new gear into sprockt hub and tighten 35 to 40 foot pounds.
Install first set of nuts on outer side of sprocket hub and thighten to 25 to 30 foot pounds. Install second set of nuts (hold inner nut with an open end wrench) and tighten to 25 to 30 foot pounds.
You will NEVER have the sprocket bolts EVER back out.
The JT Gears are available thru a search on Amazon, or MAW (Motorcycle Accessory World). I think that shipping might be cheaoer thru Amazon.
Cost is about $18 plus about $12 S&H.
I would recommend a 46 Tooth for a rider under 150 pounds, a 48 Tooth for a rider 150 to 200 pounds, and a 50 Tooth for over 200 pounds.
Since you need a longer chain anyhow, I would recomment a DID 428V O-Ring chain with 130 links (you cut to suit) This chain is rated at something like 4300#'s and is an O Ring design that keeps the dirt out and is suppost to last up to 18 times longer than stock. (the master link comes with the chain) It is about $60 plus $15 to $20 S&H at the same places as above.
The 46 tooth sprocket requires no modification to the skid guard. The 50 tooth might require a slight amount of bending and / or a few washers between the skid plate and the trailing arm on the left side.
The JT Sprocket web site is w.jtsprockets.c
The JTR 802 fits a Kawasaki G3, G4, G5, USA 1970 to 1975
I will do another post with front sprocket information.
I will see if I can get some pictures of both the 46 and 50 tooth sprocket installed as above (depending upon frustration level of me with camera and figuring out how to post them)
I hope that this will be helpful to some - It makes a HUGE difference in the TOTAL way the ATV operates.
Posted by: NJDale
Just like the kids with the big swamper tires on their pickup trucks - why did I burn out my clutch / trans etc ???
You would need a 50 tooth rear gear just to stay even with the 46 tooth, if you went from 20" to 22" diameter tires.
Doing the math: 20" X 3.14 = 62.8" Circumference / 22" X 3.14 = 69.1" Circumference
69.1 / 62.8 = 1.10 (a 10% increase in the circumferance)
46 tooth rear gear X 1.10 (to compensate for the rear tire increased circumference) = 50.6 Teeth needed.
Answer: go for the 50 Tooth rear sprocket = JTR 80250
Hope this helps.
Posted by: NJDale
Glad to be of help! No, the info did not come easy. Three or four weekends ago, I spent 15 to 20 hours looking around on line. First I found all the info for the gears at a gear manufacturer called "AFAM", but then could not find any retail distribution on them - they turned out to be owned by a Dutch company. So, then I started all over again and came up with JT Sprockets.
The front sprocket is a JTR 259 XX. I did a whole complete posting last night about it & hit the post button and the whole thing went to electronic dust heaven - server error! I won't have time tonight to redo it, but tomorrow night (Thursday) I will repost it.
Posted by: NJDale
00XJ - Glad to hear of your progress. Yes, I forgot to mention about the 52 MM center "Borehole" verses the 44 MM hub center flange. I too don't think that it will be a problem - IF, you use the 3/8" grade 8 bolts. I see more of a potential problem with the disk brake rotor hub that the chinees are trying to use as a sprocket hub. All the Japanese quad manufacturers (and aftermarket "premium" axle manufacturers) use a sprocket hub that is "pressed" onto the axle. The reason being that it eliminates the clearance "play" nescessary for a slide on sprocket. Over time, I have fears that the spline "play" will lead to sprocket failure. In addition, the use of a dick brake rotor hub as a sprocket hub leads to too small a mounting circle for the bolts to spread the torque to. In general - many potential future problems due to poor design decisions.
I think that the most probable longer term solutin will turn out to be getting used Honda 250R rear axles with gear sprockets, disk brake rotor hubs and outer wheel hubs (complete axle assembly - but without swing arm or bearing hub) off ebay. Should be about $35 to $100. However you must get a complete assembly with wheel hubs (different years have different spline counts). This looks like it would be the correct and low cost answer - but will require more research and possible test purchase and test fitting to be sure. Some time this winter (if no one before me), I will try this out and let everyone know what the right replacement answer is. Until then, I think that the JT Sprocket will be good enough - unless you are an extreme rider, jumper - in which case you will probably break something because at this price point this quad was not meant to do this.
ASSEMBLY TIP: If you are putting a new master link on a new "O ring" type chain - get two square type stove bolt nuts (probably for about 1/8" bolts) and a 1-1/2" to 2" small "C" clamp. Assemble new master link with the 4 "O rings". Slip the second side liink over the 2 pins. You should be ready to put the little clip on now - but it won't go, because to new "O rings" are too fat. Put the 2 little square nuts over the post ends and use the small clamp to compress the second side link into place. Leave it clamped that way and take a break. Come back later and have the little slider clip and needle nose pliers, ready to go. Release the clamp, take the 2 nuts off, and slip the slider on. (NO problem).
Posted by: NJDale
00XJ - Glad that someone else got the 50 tooth and can attest to how "different" the quad is. I got mine, put it together, rode it 10 minutes - this is just WRONG !!! - and it sat for 4 weeks while I researched the solution, ordered the sprocket & chain, and installed them. I just knew that I did not want to "glaze" the clutch - then they are never the same.
However, it gave me extra time to totally take everything apart and grease it.
All of the Jetmotos have vertiually NO GREASE anywhere!!! I have (2) 250's & (1) 110. None of them were lubricated ANYWHERE, except motor & transmission.
There are two types of "needle" adapters, that you can fasten onto the end of your grease gun. One is about 1/8" in diameter and has a blunt end - GREAT for lubeing ball joinst & tie rod ends !!! The other is less than 1/16" in diameter and has a very sharp end on it like a hypodermic needle - GREAT for lubing "Sealed" bearings - Front wheel bearings and rear axle bearings (on 110).
After draining the factory oil at delivery & seeing the "quality" of Chineese petrolium products - I bought a quart of brake fluid and changed the Chineese brake fluid on all 3 quads.
Posted by: NJDale
I suggest to start by looking at 1980 to 1987 Honda equiptment - it seems like most of what they "copied" was from that era and make. If not Honda, then possibly Kowasaki or Yamaha from the same general era. Sometimes pictures from ebay of stuff people are "parting out" helps.
Posted by: NJDale
The motor may be a Yamaha clone, BUT the output shaft on the motor/trans is early eighties HONDA. The front sprocket match is a JT Sprocket FRONT JTR259xx which is for a Honda early 80's - 80cc to 125cc motor. I don't think that the Chineese DESIGN anything - all that they do is copy. They did NOT disign anything for Jetmoto. They use the selection of copy parts that Jetmoto picks out from those copies that they offer to Jetmoto to pick from. If something is not of proper quality / sizing and there are problems with it, the they offer a copy of something else to replace it. They will make whatever you want - but it is all copies.
Posted by: NJDale
The front sprocket is JTF-259xx. "F" is the 3rd digit - I don't know why my fingers keep wanting to type an "R"
