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Frank ZX

XR650L with dual carbs?

11 posts in this topic

Would a dual carb set-up from a older xr or xl make more power than a stock CV carb?If so what year bike would I get it from?Looking for alittle more relilable power on a budget.Also,is there a better flowing cyl. head that will bolt on?Or would porting be the wat to go?

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The short answer is yes. The long answer is it is not worth the work involved. The dual carb air box will not fit. Spend your $$$ on a hicomp piston and a cam instead.

Someone tried something like this a few months ago and had issues with different diameter cylinder head bolts or something like that. Might have been a XL600 though. Don't remember.

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Not to mention that the dual carbs are a PITA to tune and no one seems knowledgeable nor able to help in doing so.

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Also the dual carbs had a starting twilight zone :foul: where they absolutely sucked to start at times!!

Cold they started fine, hot they started fine, but get in the zone where you just ride it for a few minutes, stop, go to restart, they blow man.

They also had a nice hiccup every once in a while where they would decide to do it at a light and make an a$$ out of ya!

You would have to then walk it to side of road to restart the thing sometimes, look like an amature. Yea, those motors ran good though, very good.

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Since the 650L has the button, I don't think that the starting issue is that big of deal. The drawback IMO is the airbox setup. If you could make it work, it would be a pretty neat setup. At the end of the day, almost anything is better for performance than the stock CV carb.

I never seemed to have too many problems with my '84 XL250R's twin carbs. But then again, that bike's problems were oil flow related, not fuel flow related!:banghead:

Now the twin setup on my '87 TT350 (one regular, one CV); THAT was a true PITA.:censored:

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You cannot simply bolt the dual carb setup onto a single carb bike. The head is different, it has dual intake ports. I got a XL600 head and dual 30mm carbs off e-bay a few months back with this swap in mind.

The dowel pins that locate the head to the cylinder are different sizes, but this is a pretty straight forward to fix. The carb routing is a pain. The XL600 airbox goes around both sides of the shock (the shock does not have a resevior).

It ended up being more than I wanted to do with my current bike, so I bought the FCR. I may try it if I get another XRL some day. The dual carb head will flow better than the single and will make more power. The dual carb are so cool, I really need another bike to try this on.

MGS

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I posted some pictures a while back in this thread a while back for someone wanting to swap in a single PD carb. Someone followed by posting pictures of a dual carb manifold that looks like it will fit on a single carb head.

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Given that the XRL carb is, in spec, bigger than the XR650R carb, does a larger carb really help top-end power, or is it just a jump in throttle response?

Dave

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OK,Ya'll talked me out of the idea.Will a 10.25:1 compression piston,cam,larger pipe,and FCR carb make a big power gain?Who make's the best cam?

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XR's only sells a 10.5-1 and there are a few on here that have the piston/cam upgrade and have said its awesome with a pumper carb im sure youll be in heaven.

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