Carb Tuning Woes

[senrak]

Those gaskets are a constant point of failure.

Put the boots back on with a thin coat of Yamabond or Threebond.

Yamabond.
Is that the same as Permatex Hi TEmp Red RTV

[senrak]

BTW, JAT (don't you just love our short hand) When you cleaned those carbs did you make sure those 3 little holes in the top of the venturi just behind the idle mixture orifice and the top of the butterfly were clean and clear?

That's where the fuel for midrange acceleration comes from.

Carb cleaner come out there. Does that count?

[BA80]

Carb cleaner come out there. Does that count?

All 3?????????

[TopCatGr58]

Those gaskets are a constant point of failure.

Put the boots back on with a thin coat of Yamabond or Threebond.

Yamabond.
Is that the same as Permatex Hi TEmp Red RTV

No, 3bond/Yamabond are not like RTV. In the 3bond you would want their 1102 series which is rated for gasoline resistance, their 1194 which is good for general gasket surfaces, oil/water, but not so much for fuel/gas!

RTV can break down when exposed to gasoline! However, if you apply it and then allow it to cure properly, it should be good enough, just check to ensure that it didn't squish out much into the INTAKE port/tube area...wipe away any excess.

Both RTV and 3bond/Ybond is a NON-hardening type gasket making sealant, with decent high temp resistance to help keep an airtight seal!

T.C.

[BA80]

Threebond is about $12 a tube. I used 1194 on my boots 4 years ago and it's still good.

[senrak]

Okay,
Replaced the rubber intake boots with RTV. Looks good. I did notice that the new boots I bought did not want to sit on the head flat. They wanted to rock back and forth slightly. Anyway they appear to be sealed.

Started the engine. Same bogginess, and high idle. Nothing changed. Pulled off the vacunm tube to the boost sensor and the idle came down to 1100 rpm.
Huh. This pressure sensor tests bad. Stays at .66 volts no matter what the pressure. Book says it should be 2-2.4 at 0, 1.6-2.0 at 200mm.
Does anyone have a good one?

[TopCatGr58]

Contact member Andreas Weiss, he's a good parts broker, fair, quick, etc.

T.C.

[senrak]

Thanks TC
Check is in the mail to Andreas this morning. He says he has good ones.
Ill post the outcome. I searched the site for boost sensor and found a couple of other guys with the same symptoms. Low voltage from that sensor must advance the ignition timing causing the increase in rpm. It would be interesting to check with a timing light.
Dale

[senrak]

Learning Every Day

Okay, I still have a vacuum leak. I didn't take the throttle shafts out when cleaning the carbs. Mistake. The seals are less than good. Throttle plate screws are a pita.
Where do I find reliable carburetor parts. Throttle plate screws, shaft seals, pilot air screw O-rings, and other rubber parts.
DW

[XJ Rob]

I bought throttle seals here....

http://www.xjbikes.com/Forums/viewtopic/t=44642.html

[senrak]

I've been to this site.
I must be missing something. I don't understand how to get hold of this guy chacal.

[D0wn5h1ft]

Butterfly shaft seals:
https://www.mikesxs.net/product/48-5021.html

Butterfly shaft screws (install with blue loctite!):
https://www.mikesxs.net/product/48-5022.html

Some people say his butterfly shaft seals are made out of junk rubber. I've been running mine for over 1000 miles and I have no vacuum leaks so I'm happy with them. Good price too.

[donebysunday]

If you pull the butterflies, be aware that the screws are staked (flattened on the ends) so they won't come out and go through your engine, so they start to turn and then get harder to turn out, careful. Mark which carb each goes into, I had $400 of work done on one of my early sets by a "PROFESSIONAL" and had to change them around until I found which went to which carb before it would idle down.

[XJ Rob]

I've been to this site.
I must be missing something. I don't understand how to get hold of this guy chacal.

info@xj4ever.com

Email him what you need and he can explain the rest of how to order and pay.

[senrak]

thanks for the replies guys. I can always count on you.