Another attempt to stop carb from overflowing

[Warwick]

Stock air screw settings are 1.5 out on the lower and 2 out on the upper carb aren't they? Check the manual to confirm. If all else is stock and in good condition, the stock settings will probably be fine and dandy. Don't forget to slacken off the throttle cables a bit when setting the tickover screws. And always check the oil pump adjustment after playing with the throttle cables of course... 

You don't need to earth the HT lead.

[sfo423]

Stock air screw settings are 1.5 out on the lower and 2 out on the upper carb aren't they? Check the manual to confirm. If all else is stock and in good condition, the stock settings will probably be fine and dandy. Don't forget to slacken off the throttle cables a bit when setting the tickover screws. And always check the oil pump adjustment after playing with the throttle cables of course... 

You don't need to earth the HT lead.

I'll give it a go tomorrow when I have time.

Could Yamaha have found a worse place to locate the air screw on the lower? My knuckles got bloody after 10 minutes.

[sfo423]

Update; I believe it was a double issue. First, as soon as I connected all hoses and tank the lower carb overflow was alive; like full throttle! I pulled the bowl while connected and even when I pushed the float up w/my hand it didn't stop the fuel from flowing. Bad seat/o-ring/needle (even though it feels like its seated well). OK.

That opened another issue. When I opened the bowl the fuel should have stopped flowing.; right? I pulled the tank and there was dribble out of the petcock. Its a new tap so I disassembled, inspected, put back together. Some of the screws were loose so I am going out on a small limb to say the tap was not 100% sealed.

Bike back on shelf waiting for me to order over priced needle kits.   

[torp]

sfo423,

I successfully used the float needle and seat that came from Japan - they were harder to get in (probably because the o-ring was new but it's cured the overflow problem.
Also it runs better now all the hoses are in the right place 

I think he's now supplying the right float bowl gasket as well so all in all it's good value for money.

TOP TIP - if you're ordering parts from Japan make sure the seller declares the value as LESS than $30 on the form, otherwise you'll get stung for Post Office charge of £8 PLUS taxes.

Also, I recently bought an ultrasonic cleaner which is big enough to take one whole carburettor. It did a brilliant job when I used it with some special carb cleaning solution.

[sfo423]

sfo423,

I successfully used the float needle and seat that came from Japan - they were harder to get in (probably because the o-ring was new but it's cured the overflow problem.
Also it runs better now all the hoses are in the right place 

I think he's now supplying the right float bowl gasket as well so all in all it's good value for money.

TOP TIP - if you're ordering parts from Japan make sure the seller declares the value as LESS than $30 on the form, otherwise you'll get stung for Post Office charge of £8 PLUS taxes.

Also, I recently bought an ultrasonic cleaner which is big enough to take one whole carburettor. It did a brilliant job when I used it with some special carb cleaning solution.

I figured I could cram the seat into the carb w/a little 2t oil but the actual seat is different; different steps and smaller hole diameter. See the picture below: oem on right and aftermarket on left:



I didn't trust it so I ordered OEM. I also need a tap rebuild kit as the fuel didn't shut off when I pulled the bowl and pushed the float up. Anyone know where I can get one?   

[ash33]

A little lapping paste on the needle then gently turn it in the seat will reseat the needle. Just be sure to wash all the paste off before re assembly.

[sfo423]

Just a quick and likely final update on this. I had a very tough time getting the bike idle and balance. Had time to work on it yesterday and the culprit appears to the non-oem emulsion tubes I got from the above posts. I put the cleaned up oem's back in and everything seemed to settle. The idle-balance is 90% 'there' and I was going to use a friends vacuum gauge to get me to the final sweet spot. 

Basically that non-oem jet kit is s**t. Only a lost $25USD.

One Q; if the tps on the lower was on backwards (tick over facing towards rear) what effect would that have on running bike? The slide would still be in properly though.   

[Warwick]

It'd explain the skinned knuckles when you were trying to adjust the tickover... 

[sfo423]

It'd explain the skinned knuckles when you were trying to adjust the tickover... 

Got that right! 

Its the way it was set up when I bought the bike and I didn't correlate it to the manual. Aside from rashed knuckles, I don't see any negative performance.

[Warwick]

No, I can't think that it'd make any difference. I didn't make the connection when you mentioned the skinned knuckles before. It'll certainly make life easier having it the right way round though .

A little mod that I find useful to stop the crud getting in from the tank and casuing overflow problems (it's always been tank crud in the needle valve rather than worn seats or O rings on every 3XV I've ever worked on) is to fit a short stub (1" say) neatly into the tap take off right at the base of the tap that feeds both the res and prime positions. The tap filter tends to bow at the base over time and allows crud and little falkes of rust to sneak past and into the fuel lines. a tightly fitted/sealed little stub means you are no longer sucking fuel right from the base of the tank and, in my experience, is a really great fix for what can be a frustrating ongoing problem. Carefully sealing any gap in the base of the filter would probably do a similar job too of course.   

[sfo423]

Since I had a bit of time today to work on the bike, I figured I'd close this thread out. The bike is sorted and idles perfectly @ 1500. The 'issue' with the inconsistent idle speed was twofold. First, the crap non-oem emulsion tubes (from e-Bay kit from Japan) were s**t. I pulled them and put in the stockers after I cleaned them up. I had major improvement, but consistent idle was not achieved. Second, (today) I tried again to finalize. The idle speed was solved by enriching on the air screw. Original settings (previous to this effort) were stock; 1.5 & 2 turns out. Now, I have both screws closer to 3/4 & 1 turn out. I 'assumed' the previous settings would work again. When the carbs are cleaned and new parts go in, you'll get more air flow (less crud and impurities).   

As always w/2stroke jetting, the issue just takes time and remembering the basics helps.

It was nice to put the plastics on again and open it up on the road!