I am putting a CBR600 into an LT250R. The motor is in and the hard part is done, except I am stuck on what to do with the carbs. Everyone tells me running individual filters on the CV carbs would have flat spots if I ever did get it to run right. On the other hand the airbox would require more frame work to get to fit and the plastic wouldn't fit as good. I was thinking of doing something like like oldsandman's I-beam setup if individual filters would work. I could do that easier. I notice he has individual filters. Anyone know if he is using stock carbs? If so, how hard was it to tune and how does it run? Did he machine his own adapters or does someone make them for that motor? I cannot find any aftermarket ones for mine. I drew some up in solidworks and was going to make them, but now I am worried it won't run right. I have a mill, lathe, tig, mig, plasma, rotary draw tube bender etc. so making stuff is just time, but I don't want to waste the whole summer away and this is a budget bike. Any advice is appreciated. My normal e-mail is jevs@charter.net if you want to use that. I can send pics if you would like to see the exact details of this issue.

Thanks,
John

 

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I would look into swapping the carbs for EFI. The late model Honda CB599's use the exact same engine as the F3, except it is injected. You should be able to pick up the setup pretty right off of a wrecked bike.

 

Not to be bashing but i think that iz the worst build i have ever seen.... WHY in the world would u cut the main brace on the bike??? You should have switched frames all together and the welds arnt that great.... Personally i think ur bike iz going to snap in half... that engine puts out alot of tourqe i know b/c i have one down in the basement.. i am fixing to start a new project after i get my lt back together in the next couple of weeks... its the same -engine but in a Off road Go-cart.. full suspention and everything.. havent decided if im building the frame myself or using a 150cc go cart i have down there already... build should be interesting.. Im gonna incorporate the motorcyle look into the bike and stuff like that.. well just thought i would give you my 2 cents... Drop that frame! i know u spent some time and effort into it but u will regret it in the long run... Oh and have u decided how ur gonna put ur gas tank back on?? Wont fit there! also your intake??? hmmm hows that gonna work? well this iz just all my Oppinion

 

Not to bash you either, but do you think I am leaving it like it is (swiss cheese) in the pictures? If so, your not qualified to answer my technical questions. The main support is getting replaced by a bolted in I-beam. I am in the process of making some individual filter adapters for the carbs. I have been told (by Factory Pro and Dyno Jet) that it can be tuned. I will just give up some bottom end, but gain top end. I am using this frame and motor because this is basically a free project for me (besides time). I know it won't be as good or as fast as a Busa powered DS650, but I also won't have wasted thousands of dollars. This is just a cheep toy for me. I will be able to ebay the leftovers for as much or more than I have in it. Heck, I bet I even make a profit when it goes on ebay when I am done with it. If I was trying to build the ultimate money pit drag race 4 wheeler then yeah, I might not pick this frame or that motor. It's just a toy, im not out to win drag races or anything. That would be stupid. We have super light 250R's running well over 100hp to the rear wheels were I live. I wouldn't stand a chance on this overweight, un extended, knobby tired machine. I will beat half the guys though, and it will be fun with no huge $$ investment to worry about. If the frame does snap. Whoopee. I weld in some reinforcements. That is why I am going to run it for a bit before I make it pretty. If there is a weak spot, I will find it. I plan to keep it as stock as possible aside from the motor. I am hopeing with skid plates I can still ride it on the trails. I had to give up some ground clearance. As for the tank fitting, the stock tank is probobly not going to happen. That will be the next hurdle to jump. Luckily I have a TIG welder, so I can make a custom tank out of aluminum. Just finding a place to stick it will be the challenge. I may actually make more than one tank in more than one place so I can get some capacity. I also thought about modifying the stock tank with some heat and possibly some plastic welding?? As for the other post I looked at the F4i motors and they seem to be totally different in the pictures I found. Not sure if the EFI would work on an F3. I hate carbs, but finding an injection system would be more money than needles, so I am going to stick with the carbs. I already ordered the uni filters and made drawings in Solidworks for the carb adaptors I am building. The stock velocity stacks will even be retained.

 

ah IC well your point iz made and i would like 2 see it when u get done... So far the gas tank is gonna be the main problem! but as far as plastics what are u going to do for those?? Stock would look good..it will be an interesting toy.. it will be fast..... when i build mine i already have a Yoshe pipe and header system for it.. so i hope mines gonna move.. its gonna be a trail Go Cart.. Upgraded suspention... everything like that also a 2 seater.. well good luck with the project inform me when done

 

The header is going to be a pain too, but I plan to split it. I will have to buy another die set for my bender or purchase some mandrel bends. I will use most of the stock header, but modify it to run 2-1 on each side and run it back just under foot pegs. I should be able to keep the pipes above the bottom of the frame so they won't get thrashed. Most people seem to run the pipes like a stock street bike right under the oil pan, but this seems like a crappy way to do it if your going to do more than drag race, plus I would have had to give up even more ground clearance, which is unacceptable. The tank will be a challenge, but I will hopefully have it running at that point so I will have some motivation. I have several other projects going so I need to get this done soon.

 

U could go down to the muffler shop and match the pipe... get it bent at the angle u want 2 then cut off your headers where they mount on the engine.. then run a real good weld on them.. so u have your pipes the way u want 2.. should cost more than 50 bucks and u got your pipes... well just an idea.. since i dont think u have a tub bender..

 

I do have a JD2 Model 4 hydraulic tube bender, but I don't have the dies for that size, so it is either buy the mandrel bends or the die set. The die set costs more, but then I can use it forever. Not sure which way I will go.

 

I would go with the one that ur going to use for life.... seems better 2 me.. who knows what u might need it for in the long run..