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Tr34 Sellorto/mikuni Carburator


aaronc70
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Hi, I just recently purchased a non-running TR-34 (still not sure if it's an '87 or '88) for $150US. It had been sitting under an open shed here in Florida for 4-5 years but apparently ran before putting it up. I cleaned all of the sludge out of the carb and petcock. I've always heard about gas turning to varnish but that's the first time I ever saw it! The bike starts and runs, but dies after 30-45 seconds. My neighbor says the float bowl isn't filling up. This makes sense to me and if that is the case I suspect the float needle. I thought I cleaned it up but it was in pretty bad shape. Anyone have any thoughts on this?

Also, any recommended Idle speed and air screw settings for the Dellorto carb would help. I'm in the Southern US, avg temperatures 10-35 deg C. At 1.5 turns out on both, it seems to be doing OK for what little time it will run.

I also saw some mention of converting to a Mikuni carb. Is this a good idea? If so, what size Mikuni and can you use the stock throttle cable and tube? Thanks for any help.

Aaron C.

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Hi Aaron,

Have a good look/cleanout of all of the passageways, if not done already.

There is a fuel filter in the banjo fitting on the fuel inlet to the carb that will need cleaning too.

Another area worth checking is the emulsion tube, or needle jet, it is a brass unit screwed into the body, above the main jet, plus the associated passageways.

The DellOrto fuel needles used to have a rubber tip, if so your's may have gone off.

There is a wire clip that connects the fuel needle to the tang of the float arms, is this in place? This would pull down the v/v when the fuel level becomes low in the float bowl.

I don't know the model of Dell Orto you have, PHBH or PHBL 26mm?

If PHBL, the pilot screw works the fuel circuit, so unscrewing this richens the mixture, start with 3.5 turns out from fully in.

The opposite for PHBH, works on the air cct so turning in (clockwise) richens the mixture. Start with 1 turn out from fully in.

Throttle needle try 2nd clip of the bottom.

Stay with the DellOrto, good carb, easy to tune.

Bye, PeterB.

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Peter,

Excellent information. I have a PHBH, I'm pretty sure it's a 26mm. I read through the Dellorto motorcycle carburator tuning guide last night and I'm thinking it may be a clogged vent line to the float bowl. I'll check this and the other things you mentioned tonight. Any recommendations for places to get parts in the US? If the float needle is rubber-tipped, I'm sure it needs replacing. Thanks again!

Aaron C.

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Peter,

Excellent information. I have a PHBH, I'm pretty sure it's a 26mm. I read through the Dellorto motorcycle carburator tuning guide last night and I'm thinking it may be a clogged vent line to the float bowl. I'll check this and the other things you mentioned tonight. Any recommendations for places to get parts in the US? If the float needle is rubber-tipped, I'm sure it needs replacing. Thanks again!

Aaron C.

Aaron,

You'll also want to drain and flush out the tank and remove the petcock. Petcocks usually have a short and taller screen filter in the tank and you'll need to see if the petcock passes enough fuel as the rubber washer behind the lever may also have gunk in it.

Jon

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Hi Aaron I have an 89 TR34 with the dellorto carb. I find mine will only run with the mixture screw all the way in. I'm at the stage now where although I haven't ridden the bike, it will happily tick over for ten minutes in the garage. I may follow a bit of Peters advice if I find its not running too good once I'm out and about.

You say your unsure if its an 87 or 88. The main difference I found is that the top of the tank and seat is white on an 87, and the 88 is blue. Also the tank stickers are white on the 87 and blue on the 88. If you want confirmation though check out lampkins beta-uk site,you can look up your frame number and there is some photos of each years model.

Rich

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I tried to post a picture but I don't think it worked. It looks like I probably have an '87 The tank is white plastic, the seat pad is a blue rubber material. Tanks for the carb info guys. YEah, I cleaned the petcock really well, had to do it a couple of times. It seems like it's flowing pretty well now. I'm actually moving right now so I don't have anymore time to mess with it for a few weeks. I'm pretty sure it's the something in the carb itself still plugged up with the varnish goo. I'll really try and work all the vent lines next time I get it apart.

Do you guys know anywhere that keeps these old, rare parts around? I talked to this guy: http://www.trialsnuts.com/Betaclear.htm

and he said he had a few things left.

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Aaron if you search through the air cooled momoshock section, there is a post named should I part it out, by Rick. He is somewhere in the US too, why not PM him, he was breaking up a bike a couple of weeks ago.

Also here in the UK we have John Lampkin and Steve Goode who may be able to help, they have both been great for my parts. Obviously postage may be pricey though.

Again if you look on the beta-uk site there is a PDF of available parts that you can search through, with prices in GB pounds.

Edited by wasntme
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