XR650L rebuild/power-up

[rx7turbo1]

A few months ago I lost my front sprocket on the interstate. It was good times...not! The countershaft teeth sheared off and the chain flopped around until I slowed down. Luckly it did not seize the rear wheel and I got home safely.

I am now halfway through my rebuild. The gearbox is back together. I decided to do the JE high compression piston ( I think it's 10.25?) and today I made a last minute purchase of a hot cam stage 1 cam. I am afraid this will now put me over the edge of the stock carb and stage 1 jet kit.

Do you guys run something similar? what are the results with stock carb and stage 1 jet kit? If not, what would be an affordable aftermarket carb? I am not sure what my current jet sizes are, but before the compression and cam upgrades I was running great on the middle clip of the main needle. This was with white bros pipe, stock headers, uni filter.

I also ported the head exhaust ports slightly and ground out the stock header welds and polished everything smooth. Things are looking nice though. Sand blasted the exterior of the head/crankcase. Looks new! I just want it to ride new but with 10+ hp ?

Thanks! -Brad

[uranys]

Brad,

My setup is very similar to yours, except that I run a supertrapp slip on.

I'm using the stock carb with a factory pro jet kit (i think the jet sizes are the same as keihin's) 55/160 at 770ft. above sea level. I've also drilled out the holes in the slide (ala daves mod's).

It works well for me. It may be a little lean on top, so I may go up to a 162, but It pulls strong with no hesitations or stumbling and doesn't backfire on decel.

I see that a lot of people use a 58 pilot when doing these mods, but I think that would be too rich (for me). My fuel screw is about 2 turns out, and starts fine if you use the choke.

I'm not sure switching to a pumper carb is going to give a big increase in HP, I think that most people switch to them to get better throttle response.

HTH

[HeadTrauma]

An inexpensive option for a non-CV carburetor would be either a 600R or 650R carb. Kenzo has a 650R carb on his 650L and he hasn't been on here cussing about it, so I guess it works well. ? I don't think the Stock 650L carb is going to hold you back that much, but the other two plain old slide types will probably make the bike feel more powerful by making the power more abrupt.

Got any pictures of the portwork you did? Did you do anything to the intake side?

[Kenzo]

u just need to make sure to bump the jets, needle and make sure piggy has plenty of air...no real need for a different carb...

i like the R carb alot...u wack it...it chits & gets...and if u can find one in gud shape w/ the throttle/cable assembly for ~$100 i'd say go for it!

$400-$500 is a bit excessive in my book for a little better throttle response and bling

that being said i'm think'n about get'n my R carb chrome plated ?

HAHAHAHAhahaaa...

[martinfan30]

You may not need to richen them up. You'll just have to watch the plug.

Or get a colortune plug.

[rx7turbo1]

Awesome, thanks guys. I never thought of using a 650r carb. I'd need to look at the choke and throttle cables to see which way they mate. Paying $400 for a carb is out of my budget after this rebuild.

I think my plan will be to see what the stock carb does with my current jets, go out for a few days and make a guess from there. From the sounds of it the CV carb can flow the fuel but is slow to react. I could live with that as long as I don't run too lean up top. I will play with the needle positions and exhaust spacers. I have already done Dave's carb mod and a lighter slide spring. I don't mind playing around with it for awhile before making the final decision of going with another carb.

Do we know what size the stock carb is? I'm measuring 43mm ID for the engine side and 58mm ID for the intake side.

Headtrauma, I had to go outside to double check, but I did port the intake ports along with the exhaust ports. Basically port matching to the manifolds and smoothing out and bumps. I left the intake somewhat rough and the exhaust smoother. I think this mod alone will be nice. I have a feeling this will behave much nicer on the top end if I can get it the desired fuel.

I'm hoping for 3rd gear wheelies! raH!?

[rx7turbo1]

Also, one mod I still have left is punching a few holes in the fender for the airbox to breathe. I should probably do that before tuning in the carb..good thinkin' Brad, good thinkin... ?

[HeadTrauma]

I can't speak for the 650L carb, but the 600R carb throat is not actually as large as the outlet that everyone measures. I suspect the 650L carb is similar, even though the official size 42.5mm.

The cylinder head is where most of the power in any piston engine lies. Imagine my surprise when I found this on my bike:

http://img.photobucket.com/albums/v521/65ShelbyClone/Public/port1.jpg

http://img.photobucket.com/albums/v521/65ShelbyClone/Public/port2.jpg

[rx7turbo1]

Headtrauma, thats some nice port work! How's it workin out for ya? I didn't do my intake side that agressive, but I did get some pics of what I did. check em out and tell me what you think.

http://www.cowwithbinoculars.com/pics/

?

[HeadTrauma]

Looks good. ?

The portwork was done by one of the previous owners so I can't compare it to stock, but it seems to work well. Whatever cam they put in maintained the bottom end torque, so it's not mushy. I don't know which shop did the porting, but I have reason to believe it was done by XR's Only.

[Kenzo]

Also, one mod I still have left is punching a few holes in the fender for the airbox to breathe. I should probably do that before tuning in the carb..good thinkin' Brad, good thinkin... ?

test the bike with & without the airbox cover/number plate before cutting holes in it...

i wud have rather not vented mine but the battery relocation mod requires it...

[rx7turbo1]

Kenzo, why don't you like the holes? because of extra trash getting to the filter? Or is there a performance reason? I found with the airbox cover off before that the bike was more unresponsive and seemed to bog more in the low end.

[Kenzo]

Kenzo, why don't you like the holes? because of extra trash getting to the filter? Or is there a performance reason? I found with the airbox cover off before that the bike was more unresponsive and seemed to bog more in the low end.

the holes make water crossing a bit sketchy...i added some Uni prefilters but wud have prefered no holes...

removing the cover was just to test if u even need the added holes...in most cases they are not required on the L and it's better to just use the stock opening...

gotta run...

?