Kpx 250 transmission goes kaboom

[Jay93]

Here we go guys! While riding my kpx yesterday something let loose in the transmission. My oil had 650mi on it and it’s level and the chain tightness were checked every 2-3 rides( my rides are 40mi-60mi). They day of the malfunction both had been checked and confirmed correct. Oil level was right below max fill and chain had 10mm-20mm of slack.

The engine runs like a top but the only gear that exists is 1st, Second is a grind fest, and third acts as a neutral(clutch out no engagement rolls freely). My bike has 9705mi on it and I bought it sept. 2022 so it’s definitely under warranty but we’ll see how venom responds. In their defense they have been nothing but great and it’s why I have any hope to ride this bike ever again! I will keep you all posted, today I sent them a video showcasing what’s happening and they said they will be in touch soon.

[JerryHawk250]

I'm sure Venom and American Lifan will stand behind its warranty.

[tknj99]

If second hadn't been grinding, i'd say to check the rear sprocket in case the studs broke.. happened on my Brozz 250 and at first appeared to be a transmission issue until i looked down while stationary and saw the rear sprocket spinning freely

[Jay93]

So venom responded with the preliminary diagnosis of gear shift lever misalignment or bent shift fork. To diagnose they told me to disassemble the engine. Wonderful. This seems weird as the engine is running amazing and all the chatter and problems seem to be coming from the transmission. I’m going to fallow their instructions to the T so they have to honor the warranty.

I told them to send detailed instructions and I would get on it. Ive never done anything like this, I’ve worked on cars my whole life and I understand the principles of how most things work on these bikes but What tools do I need for this? Anything special? I have a fairly full set of tools but nothing specialty for things like this.

Thanks tknj, I looked for the hell of it and the rear spoked is good.

I will keep you all posted, this should be interesting.

[JerryHawk250]

Just think of it as a learning experience. Probably when it's all said and done, they will send a new engine.

[Jay93]

I’m guessing I should take the engine out first then start the disassembly? I know I’ll have to take the chain off and unbolt the engine plus miscellaneous plugs and connections. If I’m going to pull this off I’ll need to conquer a pretty serious learning curve.

I’m glad I have a good community to go to with questions. A new engine/transmission assembly would be ideal and I agree that that’s probably what’s going to have to happen. My transmission sounds like a garbage disposal with a fork in it.

[JerryHawk250]

Yes, you will need to remove the engine. Take plenty of pictures and vides. They will help when putting it back together. But hopefully you will get a complete engine to put back in if the gears are destroyed. That would mean that small pieces could be lodged in oil ports which would cause more problems later. If you are lucky, it may just be the actual shifting mechanism that is either broke or misalign causing it no to shift correctly into every gear. That won't require a complete tear down and will only involve the removal of the side covers. I've seen that happen of a few Hawks on here.

You may just want to try removing the right side cover to examine first.

Here's a link to the service manual. https://drive.google.com/file/d/1C-W...usp=drive_link

[Jay93]

Thanks for the support Jerry! You’ve always been there to help I’ll start by taking off the side cover and see what’s going on in there. I’m assuming you mean the side cover on the opposite side as the gear shift lever and rear sprocket correct? I’ll be on a cross country trip the next week so I’ll have some time to get things straight in my head before I dive into the deep end of the pool.

Any one with any tips please jump in!!!

[Jay93]

Ok guys! First I’d like to thank Garie at venom for being an absolute gem to deal with. Lifan has decided to send out a new engine unit and they’re even shipping it for free! Super nice to see companies stand behind their warranty, so for anyone in the future worried about buying from Venom Motorsports, don’t worry. They really do their best to help you get your money out of a product they have no control over the manufacture of. What more could you ask for. I will keep everyone updated on the engine change but hopefully it’ll go smoothly.

[JerryHawk250]

Originally Posted by Jay93

Ok guys! First I’d like to thank Garie at venom for being an absolute gem to deal with. Lifan has decided to send out a new engine unit and they’re even shipping it for free! Super nice to see companies stand behind their warranty, so for anyone in the future worried about buying from Venom Motorsports, don’t worry. They really do their best to help you get your money out of a product they have no control over the manufacture of. What more could you ask for. I will keep everyone updated on the engine change but hopefully it’ll go smoothly.

That's awesome. They are the best dealer I have dealt with.

[TominMO]

So at 9700 miles they hand you a new motor. Very nice! If they are letting you keep the old motor, you now have a ton of spare parts. Maybe port the head on the old motor for example.

[Jay93]

Ok guys, update! Engine came UPs yesterday and I got it switched out in about 5 hours! Not too bad for my first try if I may say so myself! Fired right up and seems to run fine. Changed out the shipping oil for some conventional 4stroke 10w-40 and put about 35mi on her so far. Seems to run like a dream and shifts nice and smooth. I’ll change the oil again at about 50mi and 150mi as I did with my first engine.

Thanks to all for the encouragement and kind suggestions! For anyone wondering the engine came complete minus intake and exhaust components and mounting hardware, and the unit cost if purchased is $1099.99 plus $120 for shipping just for future reference, thankfully mine was covered under warranty.

[Thumper]

That's great news. Good warranty and stand up vendor.

I'd be real curious what you find in that transmission area. Something must have gotten loose in there and mucked it up. It typically is a very dependable engine design.

And yes, now you have a complete top end to port and polish! It sounds like you took good care of it.
Very cool

[Jay93]

Thanks thumper! The engine is definitely dependable, mine still fired up like this new one does but maybe the transmission is a weak point?

Has anyone ported the heads on this engine yet? I’d be interested depending on tools required. I’ve never done anything like porting a head, but then again last week I said the same thing about an engine change. I need to find a thread on it if there is one

[IdahoRider]

Were you able to determine what the problem with the engine was? I'm at almost 8500 miles and hope I won't have to be doing an engine replacement!