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1983 XT550 YDIS carburetor jets


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I just picked up a 1983 XT550 and plan on going through and cleaning it up over the winter. starts and runs great... until about 4000 RPM the engine cuts off. It seems like it is losing fuel. I pulled the carb (YDIS Y26PV dual carb - which I've heard can be a mess) and cleaned it up. There was a little debris in the bowl and the needle jet in the primary carb had a bit of gunk on it. I noticed that the main jet [what I believe is the main jet - short, stubby one in first photo] does not have any type of hole in it. I soaked it over night in carb cleaner and still no hole, doesn't look like there ever was one. Is this normal? 

 

The pictures below show the 3 jets and what the corresponding ports they came out of are. I have been unable to find any good info on the jets for these. Any help is appreciated. 

 

 

main jet.JPG

 

 

3 jets.JPG

 

 

bottom carb.JPG

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I think I can straighten you out here.  We're doing the exact same thing right now and over the winter.  I just picked up an '83 XT550 also.  It's been garaged for 25 years, but is in excellent shape.  I think we might be able to help each other out since we're working on the same thing.  I just finished cleaning and reassembling my carb and it went really well. They were clean, but gummed up really bad from 25 year old gas. Anyway, there are a few things I've learned about thyis carb over the past couple of days.  Most importantly, the carb was modified between the '82 J model and the '83 K model.  If you're looking at the schematic in the J model manual it shows a "secondary main jet" where, in your third photo, the read arrow labeled "main" is pointing.  

In the K model addendum the schematic is different and shows something called a "blind jet" in the same position. I believe you are holding said "blind" (no hole) in your first photo and, if the hole where your "main" arrow is pointing is threaded, it goes there. In your second photo, what you have is, top to bottom: primary needle jet with primary main jet still attached, pilot jet, and blind jet. I don't know how many changes they made to this carb during the 2 years of production, but mine is yet different than yours. I don't have a "secondary main jet" or a "blind jet. Just an unthreaded blind hole. 

So, what you're calling the main jet is actually the blind jet, and your main jet is still threaded into the bottom of your needle jet.  Hope this helps.  When you get to the point of checking your float height, let me know.  I think there was a change there too.  The manual says 27mm, but some say that's too high and it will over-flow at 27mm, and that they should be set at 34mm.  Mine were at 34mm when I checked them and I was told it ran great when it was parked 25 years ago.  So, I have that question out there on another forum and will probably leave them at 34mm and see what happens.  I have a hunch that the 27mm setting is from the first J models.

If you have any other questions, I'll check in on this thread from time to time... keep in touch!

 

Brian

Lead, SD

 

I'm going to attempt to upload a picture of my carb that I just took...

YDIS 1.JPG

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Thanks for the helpful info. I had never known about the differences between the two model years so I went and doublechecked and it turns that I have the J model. I was able to find a manual online and youre right, the jet I referred to as "main jet" is actually the "secondary main jet". I put everything back together the way I found it and am putting it back on the bike tomorrow. I'll let you know how it goes.

 

As for the floats I set them to the 26mm that is recommended in my user's manual - so that must be another difference between the two also.

 

Great find on the garaged bike, mine's probably not in quite the same condition! It will be nice to exchange questions and information through this process.

Edited by bwAnderson
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  • 5 years later...

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