I don't know, Arctra...you're pic showing that 40mm ID "joining pipe" is going to be a very "iffy" solution. Temps get pretty high here, and it's surprising what it does to the rubber components. If you're set on getting this carb to work, I'd do whatever it takes to get the intake manifold and carb spigot to match perfectly, or I think you'll have headaches with this from now on.

 

Yeah, thanks - I had read that after googling. My concern is the damage I might cause to the rest of the carb/seals/gaskets/etc. by applying that much heat. I think I would rather find another solution (see below) or just ditch the carb. I appreciate the advice though.

Sound advice. Yeah, I think I need to eliminate any potential leaks before playing with the jets/AP. My plan is to get the carb fitted properly first, then test again. I have already put the collar on the AP shaft to limit the fuel pumped and think I have it pretty close to where kbekus has it on his bike - so that should eliminate the AP as an issue. If I get the bike running again, playing with the a/f screw to get the idle right, and the needle clips to get mid-range mixture correct will be the next move. If I can't get that right I will be playing with jets.

Yeah, it is a dodgy solution. Fortunately I have made contact with a guy that might be able to fabricate up an aluminium (or aluminum for you Americans) adapter for me. If he can, that will obviously be a MUCH better solution than my proposed bodge-job. I'm just not sure how to marry up the aluminium adapter to the current spigot so it is air tight and heat resistant. I may need to use that horrible red loctite stuff which has cased me to go down this route.

Thank you all for your advice and opinions. I'll keep you posted on my progress.

 

Please remove the carb before replacing the mount (manifold).

Make it fit properly the first time.

I want to hear how it works out. I have a TM 36-68 coming on Fridady.

David

 

Patience is not my strong suit, so rather than wait for this weekend to meet my contact to fabricate a spigot adapter for me, I thought up another solution. Called up a few exhaust place till I found one willing to help me. He cut me 2 pieces of 38mm (internal diameter) aluminium exhaust tube - one 35mm long and the other 40mm long. He then stretched them to 40mm internal diameter so they fit nice and snug over the current spigot and have an external diameter of 43mm.



So this kills 2 birds with 1 stone as it gives me the extension without the need for any rubber, and increases the external diameter so it should seal up nicely on the rubber engine manifold. I will need to use a silicone or something to seal the adapter onto the spigot as there are a few small gaps I can see light through. Now I need to strip the bike down again and try fit the carb up to see which of the 2 adapters I need to use. Think I'll only get to attempt that tomorrow though.

 

Now that's interesting. If you get that sealed up 100% between the two metals, you may be on to something.

 

OK, so did I mention patience is not my strong suit? I could not resist trying to fit the carb up again with the spigot adapters so just did it. We have daylight to around 8pm at the moment so figured I would have enough daylight.

To cut a long story short, I fitted the carb up with the shorter 35mm adapter. The good news is that the adapter fits up nice and snug to the engine side mount, as it does the air boot. And it pushes the carb back nicely so it is not touching the starter anymore, and I should be able to connect the the throttle cables now.

The bad news is that the 35mm adapter seems too long now *doh*. It pushes too far back so the rubber boot of the airbox so there is a fold in the rubber, and the carb now sits too high so I cannot put the tank back on.

Check out the video I made of the fitting (if you click the YouTube link the video is in HD so it should be clearer):
http://www.youtube.com/watch?v=-mezC9Yrl6w

I have put the stock carb back in again and will take a crack at cutting the adapter back about 7mm tomorrow. Hopefully that will do the trick. I'll keep you posted.

 

Ouch!...that clearance for the fuel tank looks like it will be an issue almost regardless of what you do. I guess the sump of the tank extends in the open area for a good reason. I also wonder how that exhaust heat at the point on the carb is going to work out. The closest point is the accelerator pump, isn't it? If it is, that rubber diaphram may not like it, even though the fuel will help keep it somewhat cool, I guess. I'm impressed by your pursuit, Arctra, but a Bill Blue modded pumper looks pretty good all things considered.

 

Yeah. Others have managed to fit the carb up, so I am sure it is possible. I just need to find the right length for my spigot adapter. I've come this far, I can't give up now.

Yeah, that worries me a bit too. Again, if I can move the carb forward it will be a bit further away from the exhaust and not be a problem. Others have the carb fitted so it can't be that big a problem. Worst case scenario, I have some thermal insulation matting which I can cut a piece off and fix between the header pipe and AP. Not sure if that will have bad effects from vibration transfer or not?

Thank you, and amen to that! For anyone considering getting a carb that has not already been modded to fit the KLX250, take a good long hard look at this thread and think again. I have no direct experience with Bill's carbs, but if he has pre-modded them for you and they are smaller than the FCR35, I reckon they are actually a very good deal. If I had to do this again I would just buy one of Bill's carbs.

That being said, this is proving to be a good fun learning experience for me, and I have gained a LOT of confidence playing with my carb (and bike in general)

 

ill bet the Mikuni TM36-68 is sounding pretty good to you about now.... fits straight in with no modification needed.

Although fitting the FCR sounds like a challenge....... Stick with it, like you said others have gotten it to fit.

 

I like your effort...

TM36-68 will be here tomorrow. Dyno appointment mid next week if the carb works out. I think they can monitor air fuel ratio.

David