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Blood Sweat Tears and Grease => Engines => Topic started by: RoadRunner on Feb 17, 2019, 23:27:07

Title: XR600R/XL600R Dual Carb Question
Post by: RoadRunner on Feb 17, 2019, 23:27:07
Hello,
Maybe not the best place to ask, but I haven't gotten any other responses from more relevant forums.
I'm trying to swap a motor from an XL600R into a CB360.
I found a cheap motor in my area, its an 83 dual carb model, but it comes without the carbs.
If I'm not concerned about fitment in the frame can I use any two carbs, as long as they are linked progressively?
Is there anyway to make this motor run off one carb, and if so what is the performance loss?
Thank you.

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Title: Re: XR600R/XL600R Dual Carb Question
Post by: irk miller on Feb 18, 2019, 00:23:10
There's a way to run them with a single carb, but not too common and you would have to rig it. It all boils down to the intake. The stock carbs are linked at an angle to each other.  Not sure how difficult it would be, but maybe worth a shot.  I swapped TM33 carbs onto an F650, which has a narrow wishbone frame, so to me anything is possible.  I will say though, it may be a lot easier to just buy a set off Ebay.  Not sure the returns are worth the trouble.
Title: Re: XR600R/XL600R Dual Carb Question
Post by: wozza on Feb 18, 2019, 00:24:17
The twin carbs on a single are a pain when they get old you end up chasing your tail and twice the issues...For some reason in the 80's honda started with 2 carbs on their singles and in later years went to a single....with the 250's you pretty much buy the later single inlet mainfold and bung in a after market or OEM carb to suit the application....Just be careful as pretty sure there is/are difference between the XL and XR carbs/heads...
Title: Re: XR600R/XL600R Dual Carb Question
Post by: irk miller on Feb 18, 2019, 00:26:53
You can swap to a single port head, but the twin carbs produce more horses.
Title: Re: XR600R/XL600R Dual Carb Question
Post by: RoadRunner on Feb 18, 2019, 00:44:03
You can swap to a single port head, but the twin carbs produce more horses.
The issue I'm running into is that the dual carb setup has very few hits on ebay and the few ones they have are broken or messed up in one way or another.

What would it take to swap for a single port head? I've been reading that the headbolts are different sized?

Either way I appreciate the help.

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Title: Re: XR600R/XL600R Dual Carb Question
Post by: wozza on Feb 18, 2019, 06:22:58
you shouldn't need to swap the head...just come up with a suitable manifold to suit, as its going into a totally different frame you may have plenty of room to play with.....
https://thumpertalk.com/forums/topic/803283-1985-xr600-dual-to-single-carb-conversion/
Title: Re: XR600R/XL600R Dual Carb Question
Post by: cxman on Feb 18, 2019, 08:19:49
the twin carb setup if cleaned properly and set up well runs so good its awesome

you can put any single on it even a hsr pumper or fcr and it will only match the dual carb setup at a few different places on the powerband
Title: Re: XR600R/XL600R Dual Carb Question
Post by: RoadRunner on Feb 18, 2019, 12:31:24
I appreciate the help everyone!
I was able to source another motor with dual carbs for the same price but the thing hasn't been run in "a few years."
How difficult would it be to clean it up and get it running again?
Especially with the dual carbs?

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Title: Re: XR600R/XL600R Dual Carb Question
Post by: cxman on Feb 18, 2019, 12:32:36
pm me if you need help with the dual carb
Title: Re: XR600R/XL600R Dual Carb Question
Post by: RoadRunner on Feb 18, 2019, 20:20:30
So the local motor is $100, but it hasn't been started in years. Before I go look at it, the current owner says that kicking it seems to easy, maybe suggesting low compression?

Basically I'm expecting having to rip into this motor to figure out what's wrong.

This will be my first time ripping into a motor like this, what should I be looking for/expecting to replace?

Also, I've been looking at some other threads about souping up these motors, using parts from other bikes.

Supposedly using the cylinder and piston from a XR650, or the crank from an XR600.

Any ideas to squeeze any more power out of this engine or should I just let it be?



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Title: Re: XR600R/XL600R Dual Carb Question
Post by: Mr.E on Feb 19, 2019, 14:25:50
I'd just let it be.  Keeps it easier in parts sourcing.  You can pile on a lot of $ for a couple ponies, and the xl/xr dual carb motors are no slouch.  I will say for the 83 motor,  it's got the weirdo Reed valve in the head, so if you use a later set of dual carbs,  you may want to block that off.  Up to 87 they all had the cover on the left side of the head but the casting was empty from 84+.  If you need cam  chain and sprockets at some point,  you can also use 88+ xr600 parts,  just have to swap both sprockets and chain out at the same time.  The xr600 flywheels are a bit lighter in the 83-87 years too.  Otherwise there's barely any difference in those year motors. 88+ saw some changes, including a lower first gear.  So I'd avoid that unless you want.  As for power by themselves,  if I had a motor that are itself,  I'd consider doing some barrel up mods but till then,  I'll enjoy it being comfortable doing 100 mph in stock trim