rebuilding throttle bodies

[raz]

I guess the answer to this thread is the same type of wear, and shaft is moving with the vacuum.

[docc]

Hmm, so true. In that thread on TPS variation, Dan M suggests it may be shaft wear on the high milers.

 

How many miles (kM) on your Sport i, Raz?

[jenslh]

Sorry for crashing the party so late - just returned from the yearly family holliday....

 

The shaft in the throttle body runs in two "bronce" like bushings and they dont seem to wear, but there can be a considerable play even on brand new bikes.

 

Outside the bushings, there are rubber seals on the shaft, and they tend to harden over the years. The hardend seals is what causes the leak/drip.

 

Officially, there are no spare parts for the throttle body assembly, but I found out that the seals from a Yamaha XS650 carburettor is excactly the right size. (For 1100 sporti and V11)

 

Take great care (and photo's) when you take the throttle body's apart. There's a lot of springs and washers that must go back in the right order and orientation. - And use some loctite for the screws that are located in the air flow. You dont want the engine to guzzle one of these.

 

Good luck.

[raz]

How many miles (kM) on your Sport i, Raz?

Now 56,345 km. The figure will raise with about 5,000 in the next 14 days or so

 

The shaft in the throttle body runs in two "bronce" like bushings and they dont seem to wear, but there can be a considerable play even on brand new bikes.

 

Outside the bushings, there are rubber seals on the shaft, and they tend to harden over the years. The hardend seals is what causes the leak/drip.

 

Officially, there are no spare parts for the throttle body assembly, but I found out that the seals from a Yamaha XS650 carburettor is excactly the right size. (For 1100 sporti and V11)

 

Take great care (and photo's) when you take the throttle body's apart. There's a lot of springs and washers that must go back in the right order and orientation. - And use some loctite for the screws that are located in the air flow. You dont want the engine to guzzle one of these.

That's worthful info Jens, thank you very much! I'll try dismantling mine next winter. Do I need 4 pieces of that same seal or what?

 

I already know that the tiny screws securing the TB's to the lower and upper bars (that fixes them to each other) are bastards to remove without heat and other tricks. Without removing them, you can't take the TB's off the engine - unless you remove the engine from the frame...

[jenslh]

Do I need 4 pieces of that same seal or what?

 

I already know that the tiny screws securing the TB's to the lower and upper bars (that fixes them to each other) are bastards to remove without heat and other tricks. Without removing them, you can't take the TB's off the engine - unless you remove the engine from the frame...

 

Yes - You'll need 4 seals of the same type. As far as I remember, you buy them seperately, and they are quite cheap as they fit a lot of Jap carbs.

 

No - there's no way to remove the complete throttle body assembly in one piece as long as the engine is in the frame. The connecting bars have to be removed first.

[stormsedge]

Yes - You'll need 4 seals of the same type. As far as I remember, you buy them seperately, and they are quite cheap as they fit a lot of Jap carbs.

 

What do I call the seal when I try to look up or purchase? Thanks. k

[jenslh]

What do I call the seal when I try to look up or purchase? Thanks. k

 

No idea - its two ordinary steel/rubber seals (per carb) that is located on the shaft for the butterfly valve on the Yam 650 vacuum carb.

They look qiute like the seals on either end of the crank (but a lot smaller of course) and there should be no other seals like that in the carburettor.

[dlaing]

Probably not valuable information, so feel free to ignore, but I just pulled my TPS and the throttle pulley and lubed each at the top with silicone grease.

The low RPM popping is now gone, except for an occasional pop and stall at idle

But was the cause of the better running the silicone grease, or the changing the TPS reading from ~145mV to ~110mV and rebalancing TBs?

If the silicone grease helped it is probably only a temporary fix and the seals are what really need replacing.

Thanks Docc and Jens for bringing forth this problem cause and solution!

[mark.gilmore]

Everyone must have that same little stumble,mine is @ 2500rpm with throttle just cracked on.but not very often.

very interesting. 50,000km

[andy york]

Well, I have just installed another set of throttle bodies on the

ole girl, and she runs pretty good!

As of this moment I don't have pop and crackle any more from

2500 to 3300 rpm

The seals appear OK on the throttle shafts. I will replace them

when I find the right stuff.

The shaft itself does not appear to be worn but the bushings must be made

of the same crappy material as our valve guides. Still working on that solution.

The amount of crude that gets under the TPS is amazing.

What piss poor design. I'm thinking a little bit of silicone or a piece of

tape....something to keep water from getting under the TPS and rusting

the top of TB shaft. It appears to me that the right side is worse than the left

because of that.

If you try and disassemble the TB's on the bike, use good hex sockets...etc

because the screws are small and locktighted.

more to come....

andy

[docc]

Andy reset my CO today with the VDSTS. It has never been set since the factory. We moved it from -27 (0.15 on the gas analyzer) to 0 (0.38).

 

The idle came up into the normal range (1100 instead of 900) and the idle is much more stable now, even idling in the Nashville traffic in the heat. The popping on the over run in the lean 4000-4500 range is improved.

 

It does, however, continue to burp and pop at idle, just off idle and in the lean rang of the map. Better, but this persists.

 

I'm sure Andy is on to it with this throttle body business. I'm looking forward to the fix becoming available at Corse Motorsports.

 

Thanks, again, Andy!

[callison]

The Sport's been running awfully lean: popping on the overrun, stumbling at idle and such.

 

When I spray solvent into the spring on the bottom of the right throttle body, the idle goes up a couple hundred rpm. I presume the seal on the shaft is done.

 

Are these rebuildable with an O-ring or such?

 

Can I take it apart on the bike?

 

The seals are available through your friendly local Yamaha dealer, part number 256-14997-00. Minimum order was ten though so I wound up buying $37 worth or something like that. Worst part, I don't know for certain they're the right seals as I haven't rebuilt any throttle bodies yet. I don't remember where, when or who posted the original post either. However, if you're interested in trying some out, PM me and perhaps I can reduce my "parts inventory" a bit.

[mark.gilmore]

The seals are available through your friendly local Yamaha dealer, part number 256-14997-00. Minimum order was ten though so I wound up buying $37 worth or something like that. Worst part, I don't know for certain they're the right seals as I haven't rebuilt any throttle bodies yet. I don't remember where, when or who posted the original post either. However, if you're interested in trying some out, PM me and perhaps I can reduce my "parts inventory" a bit.

Callison,u changed out thoes seal's yet,if so,how'd u go.

[richard100t]

Probably not valuable information, so feel free to ignore, but I just pulled my TPS and the throttle pulley and lubed each at the top with silicone grease.

The low RPM popping is now gone, except for an occasional pop and stall at idle

But was the cause of the better running the silicone grease, or the changing the TPS reading from ~145mV to ~110mV and rebalancing TBs?

If the silicone grease helped it is probably only a temporary fix and the seals are what really need replacing.

Thanks Docc and Jens for bringing forth this problem cause and solution!

Well the symptoms of popping & stalling at idle are usually caused from the tb's being out of balance. The tps has to be set right as well. Everyone rides their bikes in different climates & has all different mileages, & riding styles. I dont know if these are problems with the throttle body equipment itself, but I will continue to monitor this thread with interest.

[callison]

Callison,u changed out thoes seal's yet,if so,how'd u go.

 

Not yet. I have a spare set of throttle bodies to experiment with though. That ought to alleviate my baser fears but I'm in no hurry to work on that with so many other projects in the wings.