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Old 09-24-2014, 02:39 PM   #1
KirkN OP
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'86 XL250R - Does single-carb manifold from XR250L fit?

Like the title says...

I have an 86 XL250R with the dual carbs. I'm thinking of swapping to a single-carb setup and, other than fabbing my own manifold like Stretch67 did (here: http://www.advrider.com/forums/showthread.php?t=788941 ) (which is beyond my skills anyway), does anyone know if the single-carb manifold from the '91-on XR250L will fit the '86 head? Or does it aim the carburetor to a bad spot?

Stretch, do you make those single-carb manifolds of yours on request?

Kirk
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Old 09-24-2014, 03:51 PM   #2
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Hi KirkN, I have the same year same bike, it's under reconstruction though. I don't mean to hijack the thread, but maybe we can being in some more who know. Meanwhile, what in the world do you use to get that spark plug out?
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Old 09-24-2014, 03:54 PM   #3
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http://www.amazon.com/Motion-Pro-08-.../dp/B009D35UEQ

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'83 Honda XL600R 618cc 11:1 Wiseco, XR's Only Exhaust, big tube header, 6 Sigma stage 3 carb mods

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Originally Posted by Carter Pewterschmidt View Post
He's the XL600 Jesus, his bike dies for our sins.
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Old 09-24-2014, 04:47 PM   #4
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Won't fit
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Old 09-24-2014, 05:47 PM   #5
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Fits my RFVC head.

http://www.ebay.com/itm/18MM-DEEP-SP...-/130531632735
Alternatively, he can grind down a 18MM deep well he doesn't like anymore.
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'83 Honda XL600R 618cc 11:1 Wiseco, XR's Only Exhaust, big tube header, 6 Sigma stage 3 carb mods

Quote:
Originally Posted by Carter Pewterschmidt View Post
He's the XL600 Jesus, his bike dies for our sins.
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Old 09-24-2014, 09:49 PM   #6
Stretch67
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Hi, Kirk.

I don't believe the single-carb XR250L intake will even bolt up to the XL250 dual-carb head. As you can see from my photos in the link in your post, the two inlet tracts make for a pretty wide intake, much wider than the XRL intake. I simply don't think it will work, being the reason I had to fab up mine.

My manifold works great until the engine gets hot. Then the heat from the head transfers through the short all-aluminum manifold into the carb, where the gas boils in the float bowl. It's okay as long as you don't kill the engine. If you do, then the float doesn't float, and the carb floods like the Nile valley in springtime. Much kicking ensues.

I need to redesign it with an inch of rubber between the manifold and the carb, giving it some thermal insulation from the head.

But even so, it's tons better than the old carbs and intake.
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Stretch67 screwed with this post 09-24-2014 at 10:05 PM
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Old 09-25-2014, 04:38 AM   #7
KirkN OP
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Well, that's what I was afraid of. I just wasn't totally sure.

I used to have a 93 XR250L, and I've gone back thru my pictures, and I've realized that the intake manifold on the 93 bike aims the carb out to the right, rather than to the left, like on your conversion. So, at the very least, I'd have to use the right-side intake boot instead of the left side, as you did.

What I can't tell for sure / can't remember is what the port opening / bolt pattern on the head looks like on the 93. But, I think you're probably right - the dual separate intake tracts on the 86 probably make it a lot wider than the 93's.

Ah well.

On the other hand, fabbing up a (relatively) simple flat adapter plate from the narrow opening on the 93's manifold to the wider opening on the 86's head might be within my skill-set. More like just drilling & grinding vs. welding up aluminum bits.

Hmmm..... I may have to give that more thought.

Thanks, all, for the replies.

Kirk
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Old 09-25-2014, 09:50 AM   #8
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Let us know how it turns out.
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Old 09-25-2014, 10:54 AM   #9
KirkN OP
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Well, thanks to the internet, I know a bit more, and I went ahead and bought a used manifold from a newer XR250L for 10 bucks off ebay to experiment with.

Overall, it looks like there's a fair chance that, although the intake ports are wider on the XL250R dual-carb motor, the bolt pattern looks like it might very well interchange.

Here's an XR250L single-carb intake port: note that although the intake port port opening is pretty small, the manifold bolt spacing is very wide; very like the dual-carb port's bolt spacing (which I couldn't seem to find a photo of):




Here's the backside of the single carb manifold:





And, here's the backside of the dual-carb manifold:






Let's pretend, for now, that those three bolts are spaced the same. Kind of a triangle shape.

It looks like the dual ports are much wider, and extend out beyond an imaginary line drawn between the top outer bolt holes and the center bottom hole.

But, even so, a flat adapter might be made that would allow the single port to feed both the separate ports. Flow itself would probably be terrible, though.

In either case, I'll probably tinker around with it. The thing is, my dual-carb bike is running OK right now, so that's a bit of a dis-incentive to do the swap. But, the motor is pretty whipped, blowing blue smoke most of the time, so an overhaul is in my future, I expect. Maybe then I'll tinker around.


Stretch, as for yours, I've had a number of old vintage (early 70s) Hondas that only used a hard plastic / phenolic spacer of about 1/4" to 5/16" thick between carb and manifold, and AFAIK, they never had problems with excess heat transfer. If yours were mine, I'd be inclined to make a 1/4 or 5/16" spacer out of plastic (like the plexiglass that windscreens are made of) and slip it between your carb and your self-made manifold with a gasket on either side and some slightly longer bolts. I suspect that would cure your bike's problems without really much of a space impact. You'd probably be able to squeeze / squish the air filter boot back that much without needing to re-do it all. Just my two cents.

Thanks again, for the replies.

Kirk
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Old 09-25-2014, 11:17 AM   #10
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Here's what I'm sayin':


My old '71 Honda SL100:






And an early 70s Honda CL175 with similar set-up:





And yours, from the other thread. I'm thinking a little plexiglass spacer will slip right in and do the job with minimal impact...

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Old 09-25-2014, 01:41 PM   #11
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you are not going to be happy


the single carb manifold(insulator) and the dual carb insulator share the top two bolt holes, and the alignment is the same on the bottom, but the TwinCarb insulator's center bolt is higher than the single's.


You can drill a hole in the single carb plate at the level of the Twin's, as there is all kinds of real estate to do it.


That being said, there is a GROSS misalignment of the ports, and i doubt you'll be able to make it work satisfactorily.




Since you can't find an OEM XL25oR insulator, it's BEST to use a 2 carb 84-85 XR25oR insulator, or even a 84-85 XR2ooR(twincarb) manifold.
both will directly bolt in, ports align, align with carbs etc..



When i used an XR25oR '85 plate, i also did a great deal of porting/polishing the intake tracts with a dremel..
It was easily visible, that the XL ports are the smallest of the three, the Xr2ooR are the mid's, and the XR25oR had the largest...







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Old 09-25-2014, 02:11 PM   #12
KirkN OP
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Hey, crusher, thanks for the info.

Yeah, that's what I hinted at re: the flow probably being terrible trying to adapt the singe-carb's larger, more centered single opening with that splayed-out, two-separate-intake-ports situation on the dual-carb's head.

We'll see...

Re: using some other manifold - thanks, I appreciate all the different suggestions. Makes finding suitable parts that much easier. (Actually, those photos came from an ebay auction for a NOS dual-carb manifold, only ~$150) But, I still wind up with a dual carb set-up, and part of the attraction was moving to the $35 simplicity of a single carb. No linkage to get out of whack, simpler jetting, 50% less moving parts to wear / leak / give trouble...

But, as I say, my own 250 is running pretty decently now, so it's just something I'm kicking around for when rebuild time comes.

Thanks,

Kirk
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Old 10-03-2014, 08:57 AM   #13
KirkN OP
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Well, the XR250L single-carb manifold showed up the other day.

But, I guess I'll never know about the swap now, 'cause I've decided to sell the old girl.

Anybody wanna buy an 86 XL250R?

Thanks again for the info everyone.

Kirk
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Old 10-10-2014, 02:43 PM   #14
Friedom
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Quote:
Originally Posted by RFVC600R View Post
Fits my RFVC head.

http://www.ebay.com/itm/18MM-DEEP-SP...-/130531632735
Alternatively, he can grind down a 18MM deep well he doesn't like anymore.
The motion pro tool looks way too big, and is from what I've read. Anything without a tapered shank doesn't have a chance. I was hoping to avoid grinding down an 18 DW, but I've got one hanging around, so that's my last resort.
Was going someone sold one that works. Thanks
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Old 10-10-2014, 06:35 PM   #15
RFVC600R
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You can also get the actual spark plug tool from honda
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'83 Honda XL600R 618cc 11:1 Wiseco, XR's Only Exhaust, big tube header, 6 Sigma stage 3 carb mods

Quote:
Originally Posted by Carter Pewterschmidt View Post
He's the XL600 Jesus, his bike dies for our sins.
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