Yamaha TRX850 Enthusiasts Forum

Decided to clean and check the carbys the other day, with a view to replacing the needles and emulsion tubes to try to cure the hunting at constant throttle opening between 3000 and 4000rpm. Checked the float height while it was apart, and the float was about 9mm above the throttle body! A long way from the 14mm it should be.....so, I adjusted the float to 14mm, put it all back together, and now its running like a hairy goat. Starts OK, but when I open the throttle it splutters and backfires.

Buggered up the float level I'm assuming, so pull it apart again, and reset the float height back to 9mm and only slightly better, if at all! Of course I had to adjust the TPS while it was in bits and altered the pilot screw from 1 1/2 turns out to 2 turns out So I'm not really sure what I've changed that's caused the problem.

What am I missing??? What have I done??? Why couldn't I just leave it alone??? Why am I such a dick???

I hate messing with carbs, so you have my sympathy, alter one thing at a time is the advice. When I fitted thr titanium needles I ended up messing about with the settings for two weeks and it was never quite right, ended up taking it to a dyno operator who srt it up perfectly for £75 - worth every penny IMHO

Homer wrote:Decided to clean and check the carbys the other day, with a view to replacing the needles and emulsion tubes to try to cure the hunting at constant throttle opening between 3000 and 4000rpm. Checked the float height while it was apart, and the float was about 9mm above the throttle body! A long way from the 14mm it should be.....so, I adjusted the float to 14mm, put it all back together, and now its running like a hairy goat. Starts OK, but when I open the throttle it splutters and backfires.

Buggered up the float level I'm assuming, so pull it apart again, and reset the float height back to 9mm and only slightly better, if at all! Of course I had to adjust the TPS while it was in bits and altered the pilot screw from 1 1/2 turns out to 2 turns out So I'm not really sure what I've changed that's caused the problem.

What am I missing??? What have I done??? Why couldn't I just leave it alone??? Why am I such a dick???

Don`t be hard on yourself homer, there is likely some crud around there somewhere and with the worn tubes and needles it`ll never be right anyway.
If it was me I would pull the carbs off, strip them completely but keep each carbs components seperate from the other, say in a small box of some sort so as not to mix them up.
Check EVERYTHING for wear and tear, the diaphragms for splits, remove all the jets etc, I found the choke plunger ends on my stock carbs to be badly worn when I stripped mine a few years back, they might have got that bad that they could have broken had I not noticed it when I did!
As for cleaning them thoroughly, do you have a dishwasher, good for cleaning the outsides of them up?
Alternatively a glass bowl, clean petrol and / or carb cleaner in an aerosol can. You will be amazed at how much crud can be teased out of carb drillings and air / jet passageways. Cheap budget brand cola could be used to soak the carbs in overnight, it`s a weak phosphoric acid so will take out oxidisation, remember when you bought the bike it was quite some mess, could have been crud in those carbs for years!
The glass bowl will allow you to see how much crud you get out, obviously clean fluff / lint free cloth needs to be used too upon reassembly.
The float heights are correct at around 14 mm but make sure you squeeze the off white plastic float holder up flush to the carb body (the part with the o ring on) when you take the measure ment, if you let it rest there it is often too low.
I thought to myself when I did mine, "ferk I`ve not got enough fingers"! I utilised a pair of wide gape vice grip like pliers to help hold it flush, gently clamped of course.
Have you got new emulsion tubes and needles to go in the carbs yet?

Check the factorypro website. they have data on setting the carbs up.
cheers
fung

Oh yes forgot that Fung:

http://www.factorypro.com/prod_pages/prody85.html

Some members bikes featured on their site too.

P.S.
AND Yamaha make a vicious carb cleaner.
Totally carcinagenic(use thick gloves and a ventilator) but superb.
around $20-$25 for a bottle.
cheers
fung