110 or 120?

for those experienced enough to know what sizes these refer to; I have a question about the carbs. after overhaul and *rebuilding* the rack with new shaft seals and fuel o-rings tonight I discovered something interesting

the main fuel jets in all four emulsion tubes are stamped with "120". problem is my bike is an '81 xj 650 maxim H and the factory service manual as well as chacal's catalog states I should have 110. could this have been a culprit to my unsteady vacuum sync problem? hogfiddles if you're reading this you should know what my problem is

either way: started this thread as to a question I have. how much of a change would mufflers do to jetting? "120" is for a 750cc bike and 110 is for a 650cc

here's the long story. when I purchased the bike it had original stock 650 mufflers. quickly after owning the bike, one muffler blew a rust hole straight thru so I purchased a 750 maxim exhaust system really cheap ($90 total). mounted the *new* mufflers and spot welded them in place with a short 2" steel pipe with same inside diameter. obviously the 750 collector would not fit properly so I wacked off the mufflers and only used them on my 650. sounded really good for the 4 to 2 system and has worked great for the past 3 years as the owner. plus I really like the look of my 750 mufflers slanted tip on the bike.

wondering if I should keep the "120" main fuel jets since my mufflers are off a 750 or get "110" main fuel jets?

 

the mufflers are Fine. I also don't think the 120 jet would have Anything to do with an unsteady vac.

Did you remove the intake manifolds from the head? Mine Appeared to be perfect, but when I removed them they were badly corroded and porous. When observed from the outside, looking at the seam, the paper gasket looked absolutely perfect. Have you tried raw propane around them while idling?

I bet canadian bikes of your model had the larger size jet anyway cause of the higher elevation - I know my bike is like that. if you're really worried about your mixture, and your bike is all stock, And if you have a spare airbox lid or can get one, cut some holes in it to get more air in. But if your plugs are a good color I woulnd't touch a thing.

got a Colortune? if you have one and can't get the blue to turn to orange kind of quickly, there's a vacume leak. once the intake is sealed up correctly you'll see and slightly hear the affects of the slight movement of the mixture screw. And if you don't have a colortune, get one, you won't realize how happy you are you spent the money 'till after you use it.

 

Correct; main jet sizes won't have an effect on vac sync.

Leave the 120's until you get everything else sorted; then if it's too rich up in the upper RPMs you can always go with the 110s. I doubt it will present a problem for you sticking with the 120s.

 

alright. well I plan to get new main jets anyways so thinking I should get the 110. we'll go from there.

fitz: here's a quote from you regarding my main jets about 2 months ago. remember saying this? lol

for $25 its worth trying something with better jets. chacal, get ready for an order from me!

 

lol i remember that too, but I had no idea the two posts were related, I'm sure neither did Fitz. What we said about the sizes is true, not about that think that looks like it would start roaring rapids lol