Greetings, and thanks to the fellows who responded to my earlier post about valve adjustment. I believe I've got the valves spot on, but now other problems arise, such as my carburetor. I've got the stock Keihin that hasn't been rebuilt, at least that I know of. I have had to deal with the hard starting, idling problems, etc. It usually is hard starting at first, but once it's good and warm it runs reasonably well, and starts again after I shut it down. I do have to fiddle with the throttle adjust handscrew a bit to get it to idle.

Today I kicked it over and it eventually started on full choke and buzzed nicely at high RPMs, as it should. However when I go to half choke it dies. I've gotten it started from half choke a couple of times, but it dies when I shut the choke off all the way. Previously I would crank the throttle adjustment higher until it warmed up. Now it will not idle, and I can barely keep it running by twisting the throttle. Dies when I let go...

SOOO, what's the opinions about rebuilding what I've got versus the Edelbrock pumper, Mikuni slide, and other carbs available? I'm getting old, and I'm really wanting to start it up and have it idle with minimal hassle (who doesn't I guess!). Help will be appreciated!

The stock XRR carb when set up and jetted properly works pretty well on these bikes and they start nice and easy.   Pumper carbs are nice for throttle response but they won't make it start any easier then a well set up stocker.   Need more info as to help ie: uncorked?, what jetting, elevation, etc.   Baseline uncorking is a 68s pilot, 175 main and the needle on the middle clip.     I have an edelbrock on mine just for the flooding issue when dropped but the stocker was really easy to start and it ran great.

Nothing was mentioned about what jets and settings the carb has now, so I'm going to suggest pulling it off the bike, disassembling, thoroughly cleaning, and in the process, finding out what jets are in it, how many turns out the idle mixture screw is, making sure the ACV diaphragm is intact, no missing parts, etc.

Just from the symptoms you describe, there is not enough fuel moving through the idle and/or pilot circuits. Perhaps even the main circuit is affected.

Thanks guys, I'll pull the carb and clean it out. It's been uncorked, I ride mostly at sea level up to maybe 5,000' at times-mostly desert riding.

I don't know what size jets are installed or where the clip is, but I'm going to learn. Would you suggest a rebuild kit or would a cleaning be enough? If I take it all apart I may as well rebuild it, but do you think I need to? The bike has sat unridden for up to a year at a time...

Did you get this figured out ?

The stock carb is junk.

weskc35k, on 01 March 2012 - 03:08 AM, said:

Pretty direct comments but I would have to agree.  Although I have an L I have tried using the R carb on it and while its marginally better than the CV carb of the L the throttle lag is very noticeable.  Throttle response is IMO greatly lagging.  I love this new FCR-MX pumper carb and would never EVER run a R or L without one.

Got any pictures of the fcr swap on a 650r?  Seems like we always hear about it being done, but never any pictures of the work being done to fit the tank around it - I'd sure appreciate seeing how you pulled it off.  Also, I can't remember if I heard correctly that the cam chain tensioner is in the way - is this the case?  Thanks!

weskc35k, on 01 March 2012 - 03:08 AM, said:

Yours might be junk but mines isn't... bike starts first time hot or cold and she runs great what else could you ask for ?......

XRMauser, on 04 March 2012 - 01:31 AM, said:

Have you tried one of these bikes that had a pumper carb?  I just can believe how it changed my bike.  To say that the stock carb is junk is unfair because it does a very adequate job at what it was designed to do but If your an aggressive driver like myself than you owe it to yourself to try a pumper out.  When you do you'll come back here and tell everyone how much the stock carb  is "junk"!! LOL

Edited by D0T-C0M, 05 March 2012 - 04:21 AM.

XRMauser, on 04 March 2012 - 01:31 AM, said:

A pumper that doesn't bog on woops and big G outs,and i've got that.
The stock carb is junk.

Ok; Ive gotten good info on the Pumper carbs, I have a 85 XL 600,dual carbs. If I were to get ,say a FCR MX 41 would I need two or would one be enough?

loom34432, on 05 March 2012 - 04:44 PM, said:

Hmmmm you'd only need one but it would require you to change the intake boot to that of the XR650L that would accept one carb.   you'd have to read up to see if anyone has done this before spending the $$$ only to find out that something doesn't fit.

loom34432, on 05 March 2012 - 04:44 PM, said:

You'll need the single carb head matey.

kburns737, on 01 March 2012 - 02:46 PM, said:

The tricky part of the swap is re-shaping the gas tank. It helps to have an aftermarket tank as the stocker is apparently made of thicker plastic. I re-shaped mine using a $12 heat gun from Harbor Freight and a wooden hammer handle. Its very important to take your time and slowly re-shape with moderate even applications of heat. The carb still needs to be installed tilted to the side a bit to clear the CCT. Its all worth the trouble as the FCR is an amazing upgrade. The bike should have come stock with this carb.

loom34432, on 05 March 2012 - 04:44 PM, said:

The FCR upgrade is going to cost more than your bike is worth isn't it??

Go through and clean the carb. Get it jetted for your conditions.  You can get them to run just fine.  Sure it doesn't respond like my 450X did but it runs great now that I've worked on it.  Besides, $700-$800 is a lot to spend on a carb!!

Edited by pb1963, 06 March 2012 - 11:23 AM.

Alright so it can be titled just slightly and everything clears and it doesn't effect the carb at all?  Very cool!  I've got an IMS tank and a pretty decent milwaukee heat gun - but I'm definitely reluctant to try and reshape it.  I guess if there's no way around it though, then it must be done.  Do you have any pictures of where exactly the tank is being altered or know of any pics on the web?  Thanks for the info on this - I did the suspension on the pig last winter and it made a huge difference - now I just need to get the fcr going and it'll be a new bike!

The dual carb setup was the best full range carburation the XR/XL's ever had, and doubtful that a pumper is going to be significantly better.
That WAS the early "pumper carb". Kinda sorta.  

kburns737, on 06 March 2012 - 02:13 PM, said:

The best way to see where the tank needs to be re-shaped is to install the FCR on the bike and then try putting the tank back on. You'll see where it needs to be massaged in to clear the throttle cable assembly.