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Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
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  #1  
Old 6 Oct 2006
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Carb Help Needed

Guys,

On the secondry carb is an upward facing tube connection that works the slide, where does this connect to and is it positive pressure or vacuum????

The airbox has been removed and 2 pancake filters installed. When i turn the throttle full the slide doesn't move!!!!

Cheers

Paul
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Old 6 Oct 2006
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Ignore the last post I was having a senior moment

The problem I'm having is the bike wont pull strongly from about 4500 rpm, taking the airfilters off and looking at the slides the secondry slide doesn't lift smoothly (although it isn't sticking) it sort of bobs up and down just short of half open. The diapragm is ok

I am at a loss

Any help would be appreciated

Thanks

P
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Old 6 Oct 2006
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Mysterious carbs

What bike do you have exactly?
On the right hand carb there is two connections, (A) one for air pressure = 'connected' to air filter outlet or outside air respectively and, (B) just upstream of the rubber connection to the cyl head there is a connection for a small hose that goes to the mixture enriching device (valve) on the primary carb.

(A) provides the higher pressure on one side of the mebrane to lift the slide of the second stage, as under the slide there wil be lower pressure that is 'communicated' to the other side of the membrane via the small vertical hole in the slide.

If the bike is stationary, ie. you are not loading th engine, there is no way you'll be able to keep the second carb open, as the load is just never sufficient to provide a sufficient airflow through the second carb. So, for me there is no proof your second stage is malfunctioning.

Are the airfilters clean and large enough? Try a short stretch without and see what happens?

I hope the description above is understandable, it is late in the afternoon and description of carbs in text I find difficult at the best of times.

Auke
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Old 6 Oct 2006
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Thanks Auke,

Sorry for the poor description, re read it my self and it only just makes sense

Its a 1991 XTZ660 Tenere, the airbox has been removed and most of the bodywork also.

I've recently had new camchain and guides fitted, but while the guy did a good job on the engine he didn't look at the carbs.

I had the carbs off today and gave them a bit of a clean out and its getting a bit better, i will try it under load on the way home from work tonight. I think the problem was a bit of cack got in there when i ran out of petrol (forgot to take it off reserve)

Again, sorry for being so vauge.

Thanks for the help

Paul
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Old 6 Oct 2006
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Hi Paul

Could be fuel starvation, you did say you ran out of fuel, this may have caused partial blockages - check petcock (and filter if it has one), any in line filters, kinked hose, fuel link hose between primary carb float bowl and secondary carb, finally check filter that sits above the inlet valve to the primary carb float bowl (you will have to remove valve body - one screw, filter sits on top of it).
I'm giving this advice on the assumption your set up is the same as on my MZ Baghira - XTZ660 engine.

Best of luck

Alec
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Old 6 Oct 2006
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Smile

Paul

The final item (valve) I refered to in the last post, is item no 43 in the attached pic :-


http://i103.photobucket.com/albums/m...tlout/h-06.gif

Again, best of luck

Alec
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Old 9 Oct 2006
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HI Alec,

Thanks for the help (my works server wont let me look at the pic could you mail it to me on please)

I put a single dose of Redex carb cleaner in and its starting to get better, i think i'll add a bit more before my long ride out this weekend and see how it goes

Thanks for the help all. I hope to return the favour one day

Paul

Last edited by chipompom; 10 Oct 2006 at 08:05.
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Old 9 Oct 2006
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Hi paul

EMail sent

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Old 10 Oct 2006
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Cheers Alec, It all make sense now. many thanks

Paul
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