Tomos A55 jet size?

What size jet is in a stock Tomos A55 carburator?

Re: Tomos A55 jet size?

B r e n d a n C a m p b e l l /

i am not sure...but i am new to the game and am wondering what jet size you would want to use after replacing the stock exhaust with a biturbo. someone probably knows the answer to both questions.

Re: Tomos A55 jet size?

my arrow has a 55 main jet/

Re: Tomos A55 jet size?

I've got the 2008 ST and the main jet is size 55, I put in a 58 and a biturbo exhaust and the difference is very noticeable. The bike no longer shutters at high speeds when going down long steep hills.

Re: Tomos A55 jet size & 4-stroking

That's what I'm trying to figure out. I have a new LX, all stock, and it seems to be on the ragged edge of 4-stroking. Sometimes it runs great, with a smooth WAAAAAAAAA sound, and sometimes it has a harsh tone and more vibration. I ran it at WOT for a mile with the harsh tone, then immediately checked the plug -- it was brown. Can anyone tell me what actually causes 4-stroking? Is it a mixture too lean, or too rich, or either?

Re: Tomos A55 jet size & 4-stroking

B r e n d a n C a m p b e l l /

the ST and sprint are identical besides the directionals, right?

Re: Tomos A55 jet size & 4-stroking

Raymond Wright IV /

its a 55.

definetly change it to a 58.

my friend did this and you notice the difference.

even with the biturbo, do a 58 or 60 jet.

Re: Tomos A55 jet size & 4-stroking

i did this to mine and didnt notice any difference other than a major top speed increase. also, mine does the same thing, sometimes it rides smooth, others it vibrates like crazy.

Re: Tomos A55 jet size & 4-stroking

Right, LX and Sprint are the same except for directionals, oil injection, and appearance features.

Re: Tomos A55 jet size & 4-stroking

Evan --

I just happened to see a post on the Tomos forum that said the A55 carb has a mixture adjustment screw. So I tried tweaking it, and solved my run good / run rough problem. I took the bike out on a long stretch of flat road, ran it until it started running rough, backed the screw out 1/4 turn (roughness was worse, as I expected), then started turning the screw back in by 1/4 turn increments until it consistently ran smooth. You might try that and see if you can optimize your carb adjustment.

Re: Tomos A55 jet size & 4-stroking

I put a biturbo on my 08 sprint, and kept the jet's the same. Maybe 5mph top speed increase.

I put on a high flow intake as well, and upjetted from 55 to 58, but did not upjet my idle (which stock is 28) and i could hardly get the bike to run - it fourstroked like crazy.

Once I get the idle jet, i think the bike will be sweet and run great.

47steve - are you talking about the air mixture screw next to the idle screw?

Re: Tomos A55 jet size & altitude

Conrad Conrad /

does anyone know how much altitude effects jetting? would 58 or 60 be enough?

Re: Tomos A55 jet size & 4-stroking

No, I'm not confused about the idle speed screw. It's got kind of a knurled knob on it so you can turn it with your fingers. And it has exactly the effect you would expect. The mixture screw is slightly recessed and is next to the carb air inlet. But I'm still not fully satisfied with the bike's tuning. It's all stock, with about 550 km on the odometer. I thought I had it pretty good, then this afternoon I took it out for a long ride -- 32 miles round trip. It ran great for the first 10 miles or so -- cruised fast and smooth at wide open throttle. Then it developed some extra vibration, made more of a coarse roaring sound (perhaps most of which was coming from the intake) and lost about 3 or 4 MPH. Got to the destination, ate dinner, and then started back home. Again, it ran great at first, then repeated the symptoms. When this happens, it seems like the bike will run well for quite a distance, but upon slowing down for an intersection or a turn, it will develop the vibration as I accelerate back to top speed, and then it won't settle down until the bike has been parked for a while. On the return trip, I stopped twice and turned the adjustment screw in (clockwise) about 1/8 turn each time, to no effect.

I'd really like to get it to run fast and smooth consistently. Any suggestions?

Re: Tomos A55 jet size & altitude

I have a 2006 Revival TS, so far I've:

Changed rear sprocket to a 24 tooth.

Installed a Biturbo pipe.

Replaced air box with Uni Pod high flow filter.

What I don't get is why there seems to be no

noticable difference between a 60 jet, 62 jet,

and a 64Jet? Top speed remains at approx 36

mph. How large a jet is required before it starts

to gag on gas? I would expect at that point I

should use the last jet that didnt gag.

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