Matching carburetor to engine

[timoteo539]

I have a '79 engine to put into an '80 bike. Can I use the '80 carb for it? I do not have a spare '79 carb. The '80 engine is frozen.
Thanks
Tim

[donebysunday]

Yes !
You may find that you want to change jetting to account for air filter and exhaust.
Check the valves, sync the carbs and go nice and easy at first. As you get confident in the new engine being strong (trans too), wring it out in a safe cop free zone. Adjust as you see fit.

[crazy steve]

Just remember that jetting and carb parts follow the carbs, not the motor. You may have to adjust the jetting, but at least try the stock jets to start.

[Bonz]

DBS, whatare you meaning by "change the jetting to account for air filter and the exhaust"? Does the bike have something other than a stock system and airbox? Or are you saying to take jetting into account if there is an intake/ exhaust other than stock?

Otherwise, just as was pointed out, he should jet the carbs for their model year, not the engines model year.

timoteo539, FWIW, 78-79 carbs are jetted very different than 80+ due to the internal structure of the carbs.

[BA80]

Bigfoot runs the later 80 carbs on his 79 and it runs fine. I personally prefer the early carbs though.

[donebysunday]

Thanks to Bonz caught the confusion in what I said about tuning for air filter and exhaust, your carbs were already running on this 80 engine, RIGHT ?

If not do you know why the engine froze ?

Start with stock jetting for 80 carbs follow the book/advice for this year carbs, engine is 79 follow book/advice for 79 engine.

Usually stock carb jetting will run pretty good, good place to start, check/read the plugs.

No matter year of carbs they were built to supply the right air fuel for an XS1100 engine

What are you doing for advance, TCI ?

[Schming]

Usually stock carb jetting will run pretty good, good place to start, check/read the plugs.

IMHO, and after all the queries on what jets to use for this or that mod, the above advice is the only way to determine proper jetting.

Riding habits, climate, terrain, cargo or not, two up or not, etc. on a stock setup will affect plug color so what worked for this bike may or mayn't work for another.

And yes, Done is spot on, these bikes will run real well with stock jetting . . . til a free flowing air filter and /or an opened up exhaust demands more but plug chops take the guess work out of the equation.

[BA80]

79 carbs and 80 carbs are of different design and use different jet sizes so following 79 jetting recommendations will put you WAYY off using that theory.

I only went up 1 size on pilots and mains on my 79 engine and carbs with the Mack 4 into 2 and it's REAL close. Probably could have gone 2 but .......baby steps.