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Mixture problems

PostAuthor: Fruid » Mon Jul 08, 2019 1:51 am

So I finally got my 84 TR1 up and running but can't seem to get it to run sweet.

Image
It has a hand built exhaust which is more or less open and a K&N filter on the side. I upped the jets to 132 rear and 130 front but, it started easily (hardly any choke) and ran without any popping or bogging but the front cylinder was running rich and It wasn't giving the power it should. Rear cylinder , going off plug colour was good even though it has the bigger jet.
So yesterday I pulled the carbs and went down 2 sizes on both to 128 front and 130 rear. Now it surges at 1/4 throttle but once the revs pick up it goes much stronger, how it should be..hit 80mph quite quick. Needs full choke to start now.
Rear looks lean if anything so I might put that back to a 132, front slightly rich but better than before.
So does anyone know why I'm getting a rich front cylinder when it's got the smaller jet?

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Re: Mixture problems

PostAuthor: Flyingdog » Mon Jul 08, 2019 7:05 am

Fruid wrote:So does anyone know why I'm getting a rich front cylinder when it's got the smaller jet?


I'll take a stab at it....
Without getting into bunch other stuff at this point, like: if I remember those, kinda like some 920s, they are jetting backwards from from the way I approach jetting Hitachi. Something like OEM: #2 @ #124 and #1 @ #126 or something like that. Most bigger Viragos lean toward (jet-wise) larger front, smaller rear. But, as in yours, you're larger than stock. Not sure why some of the earlier models were like that, maybe something to do with temps, humidity etc over there. Or cuz they were some of the earlier Viragos and decided they goofed and changed jet directions. Coarse I never got involved with Hitachi till a tick after mid 80s :bg: But I digress, just addressing the question, maybe look at the needle jet and/or the air jet. Being they are soft brass, possibly could be severely outta round and/or bleed holes plugged on the needle jet. Specially the #2 carb. Didn't you also drill the vacuum piston's holes? Maybe I'm thinking of someone else.
Last edited by Flyingdog on Mon Jul 08, 2019 8:18 am, edited 1 time in total.
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Re: Mixture problems

PostAuthor: Fruid » Mon Jul 08, 2019 8:13 am

Well the needles are different for all the models, it's a minefield really. The TR1 needles i had were a mess so i fitted some XV750 ones yesterday thinking that might be the problem but didn't really make much difference.
The manual states all of them have a bigger main jet in the rear (to help keep cool) apart from a couple that have the same. I think I'll put a bigger one in the rear still and see if I can 't get a better tune that way.

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Re: Mixture problems

PostAuthor: Flyingdog » Mon Jul 08, 2019 8:24 am

Wasn't talking bout the needles, talk'n bout the "needle jets". AKA: emulsion tubes. If they're fubar, the A/F to any particular cylinder will be messed up. Specially if the series of holes in the tubes are plugged or the outlet is outta round... will definitely cause richness. Those holes bleed air into fuel the mains let in and an mess up outlet will let too much fuel pass the needle as it rises.
Most of the time surging at low throttle, then picking up beyond a certain point is usually being rich on the low side.
Good luck anyway.
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Re: Mixture problems

PostAuthor: Hellgate » Mon Jul 08, 2019 10:27 am

Got back to stock settings a begin there. That way you have a known to begin from. Then make changes one at a time. I assume the cards are fully rebuilt?
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Re: Mixture problems

PostAuthor: Flyingdog » Mon Jul 08, 2019 11:14 am

Hellgate wrote:Got back to stock settings a begin there. That way you have a known to begin from.


Definitely agree on that one. I'm a firm believer start doing a proper "plug chop" from then on. There's no way, you can use the same plugs, going out for a ride, pull the plugs for a read, adjust, go out again, pull the same plugs, very many times in a row. Once they're colored..they are colored. Not too many know how to read plug that has been colored previously.
I'd be curious where this "larger jet for #1 carb" for "cooling" started. No shop I've worked in thought that way (but that don't mean anything), also, don't ever recall a manual talking about it. Coarse, manuals are guidelines, not gospel on lotta things. :bg: And my curiosity came about when I first noticed this with the inline fours. (inner two= smaller jets)
Oh Well.. if it works for some, I always say go for it. I personally go the other route....always worked for me.

Oh Yea..Fruid...Nice clean look'n bike. Even if I'm not a bobber/cafe person.
Last edited by Flyingdog on Mon Jul 08, 2019 1:37 pm, edited 1 time in total.
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Re: Mixture problems

PostAuthor: Fruid » Mon Jul 08, 2019 11:36 am

Thanks guys.
Yes I rebuilt the TR1 carbs and went from stock like you advise. It was running really lean and hardly rideable so I went up with the jets and that worked really well but like I say the front was rich (black and sooty plug)
the rear was light brown with the white ceramic centre showing clean.
When I pulled them yesterday I noticed the needles were different lengths, (these are new needles that came with the rebuild kit) well one was not sitting all the way down in the seat because the plastic part on the top wouldn't let it , it was too big.
So I got out my Haynes manual and the needles for a TR1 are different to any other Virago esq bike.. I put a set of XV750 ones I had rather than sanding down the plastic on the new ones.
The emulsion tubes are new from the kit as is everything in the carbs.
The manual states that some have larger rear jets and some are both the same. I know on old Ducati's this was to keep the rear cylinder cool.
I don't think its far off but I might put those new needles back in with some work to the plastic top.
I did notice the diaphragms on the slides I have are quite floppy/baggy compared to my spare set which were actually quite difficult to get to seat in the carb top.

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Re: Mixture problems

PostAuthor: Flyingdog » Mon Jul 08, 2019 11:55 am

Fruid wrote:The emulsion tubes are new from the kit as is everything in the carbs.


Well..that settles that on my thought. :cl:
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