Well, I wanted the Big Bore Kit done to my 1999 KX250 and I got it done. Kustom Kraft did the work and bored it to 74mm so it is a 310cc now. Marvin was great to deal with and think highly of him. So anyway, I have broken in my new bottom end and the new cylinder and have about 100 miles on it now. I am always searching for more gears though but it just doesn't seem that fast to me. The thing seems to want to push the exhaust pipe out of the of the engine when I rev it too. Not sure what that is all about but seems odd. I added another spring to try and fix that issue or problem. The thing is that my 01 RM250 seems faster now to me. More responsive and quick. Just don't feel like I am getting the proper power out of the thing like I should be getting. Does anyone have any suggestions? I have read about retarding the timing which I am not sure if it works or what it does? What does it do to the performance of the motor? Would like to know what others have done for the Main Jet size and the Pilot jet size that worked for them? I read in another forum that says that Eric Gorr stopped doing the 310cc because of the lack of pistons for it. They are getting hard to get and very expensive too...so I can see why. Then it says that Kustom Kraft can do the job, but they don't do the porting like Eric does, that make it work well. Wondering if that is the problem or what? Is this a common thing or issue with Kustom Kraft's work? I just want my KX310 to rip like it should. I have a K&N Air Filter, VForce3 reeds, Bills pipe, FMF shorty exhaust and much, much more on this bike. I just need this bike to work great because I have dumped a lot into it. Also does anyone know if rims for a 2002 KX250 will fit on my 1999 KX? Thanks for your time.

OK I guess I will try. First the rims fit. Now the motor is another story. You don't know me since your new here but I have a 99 KX that I had Eric Gorr make a 310 3 or 4 years ago, I also have another 310 I got off ebay that is ported the same as Erics and I have a LASleeve 300 (73mm) that is ported like you KK cylinder as they use the second over bore 300 piston. Erics porting uses a piston that you can't get anymore.

I have played with these motors a lot and have found that they all are different and what I think doesn't allways work. I have found pipes matter and don't do what I think they should. I have 6 pipes and try them all on each motor and get different results for each motor. When I put my first EG motor together I used the PC pipe I was using on the 250 and it ran OK but didn't rev well. I was thinking it's a bigbore and that is the way they work. One day just for fun I put the stock 99 pipe on and WOW all of a sudden it ripped, like wow it just got the slickest port job you can get. I screwed around some more and kept going back to that setup.

OK to yours, like I have said they all are different and like diff things. The LASleeve motor that I'm sure is ported like yours likes the PC pipe,a rad valve and very lean jetting. You need to try as many combos as you can,test,test and more testing. I have tried many conbos and sometimes get myself confused lol. Just keep tring things and take notes.

BTW I have found that an old Noleen pipe works the best on most all of them but I only have one of those. If you have questions just ask. Good luck.

Ed

What gearing are you running?

Stock gearing in the trans and the stock teeth on the sprockets too.

Reply to no1clyde: I will try the different jets and sizes to see what works better. The pipe is interesting too as I never though about that as being a possibility. For some reason I thought a pipe is a pipe as long as it isn't all dented up. So I will keep trying things as I really do love this bike. I don't ride in the winter here in Alaska so I have all winter to get it dialed in. Did your other KX310 that you have, was it like a huge difference to you than when it was 250cc? Like were you scared of its power? I am just not impressed with mine KX310....yet! Maybe I should get a old CR500 if all else fails. It's not like I am that great or anything but I am really liking hill climbing and I need the power to do the steeper hills up here in Alaska. Thanks for your time.

No I'm not scared of the power and the 300 that is ported like the one you have is the sweetest trail bike I have. The 310s when tuned right rip but are just fast powerful 250s. If you want a 500 put a KX 500 in your 99 frame, many have done that.

When tuned good they are alot of fun but I too have thought of putting a 500 in one of mine for a desert bike so I can get that 100mph speed but so far my brain (and wife) say no.

I am sure you can get your bike to run well but it may never give you what you hpoe for. Just mess with it and have fun with it.

Ed

BTW I have found that an old Noleen pipe works the best on most all of them but I only have one of those. If you have questions just ask. Good luck.

Ed[/QUOTE]

You don't know where I can purchase one of the Noleen Pipes at do you :banghead:? If you do know were please send me the links to any website or anything that would work. That be cool. I have looked and don't really see any online by Googling the name Noleen Racing Exhausts, as the company no longer does Pipes I guess. I think they just do suspensions now. I have a Bills pipe on mine currently but hope to get it all dialed in for this coming summer. Thanks again for your reply.
[url]http://www.youtube.com/user/akliving4now[/url]
This is my youtube page if you care to look.

I have Finally, got this KX310 working great after fixing the jetting issue/problem. It is Very fast and I am extremely happy with this big bore kit now. It took a while but love it, love it, love it!! I just fixed my front shocks too so now I can start jumping again. It has been like 2 years for me and I am way past over due. I would recommend anyone that is interested in getting the big bore kit done to do it. I don't have a overheating problem either like some have said and the bike it working great. Get out there and ride! I bought the Go Pro Hero HD helmet cam and this helmet cam is unbelievable. If you want to get videos of your riding go buy one of these...you want regret it! I can record 1080 HD for 4 and a half hours with the 32gb card.

Glad to see you hung in there. You do have to tune these motor but they are a blast when they start coming around. I was up riding in Idaho not too long ago and had my 01 KX300 with me and my KTM525. I was riding the 525 then switched to the KX and had SO much fun I didn't ride the 525 again that week. The 525 is great in the desert and OK in the mountains but the KX is awsome in the mountains.

I also took that KX300 to 5MOH in Utah and it was Great!!! I also have never had any of my bigbores over heat or even come close. I am guessing you had to go quite abit leaner with your bike. On my 01 300 (the one I have ported most like yours) I have been using a 02 stock pipe lately and it likes it alot.

I just got a ContourHD and am trying to learn to use it LOL, as some of you know I'm challenged LOL.

Akstyle I am glad your happy with your bike and are having fun with it.

Ed

Thanks no1clyde. I even started riding in the winter time too. So fun and it hooks up nicely with the screws. Hope your summer is going well.