FCR's and TPS advice

[misterdimwiddy]

Have just splashed all my Christmas shopping money on a set of new FCR's.



Fitted successfully this afternoon out in the freezing cold but failed to get it fired up while priming the carbs before the battery was dead. Accelerator pumps were just starting to work and it fired briefly so things look promising.

Strange things going on with the TPS however which is where I need guidance.

Removed from old carbs as instructed, fitted unit no problem to Keihins and did the Haynes test as below.

Turn ign on; unplug TPS and tacho should read 4k rpm.

Mine now reads 3k no matter where I position the TPS within its range of adjustment. Reconnected TPS plug.

Also now with TPS reconnected and the ignition on, the tacho intermittently rises to 3k and then drops back as it did when first disconnected. Have yet to check TPS coil resistances.

Before I removed it from the old carbs, TPS test showed 1k rpm on tacho, not 4k which made me think that perhaps it was not positioned right originally. Bike runs perfectly; however can be a pig to start though only when cold.

Any suggestions would be much appreciated.

[Mincehead]

The varience could be a poor connection somewhere at least it`s working! Of more interest is your cold starting issue, it can be indicative of poorly seating valves and that of course can be due to the warpage / pocketing / stretching (the verdicts out) of the inlet valves.

[Killerwhale]

Any suggestions would be much appreciated.

First off, i have not checked TPS since i put the FCR´s on but something say that there where another order getting into TPS diag...
I would do the TPS mod and forget about it

[trixynut]

If your tps is now doing the 0 to 3k cycle when connected, it believes its not connected. Check it all again. They are.fiddly to set up.
Cold starting not usually a trx issue. Do you turn tap to prime then back to on, choke out, twist throttle once, then just press starter. Works every time for me.

[misterdimwiddy]

Any suggestions would be much appreciated.

First off, i have not checked TPS since i put the FCR´s on but something say that there where another order getting into TPS diag...
I would do the TPS mod and forget about it

Killerwhale

Are you running with TPS removed and CDi mod? Can I expect some poor throttle response at the lower end as a result of permanent shift in ign timing? Seems there is mention of this in other TPS threads via search.

Trixynut

I do usually fire it up on prime and then switch to on. Always has been reluctant when cold and used to fire up on one side first before 878 rebuild. Seems to be fuel related; wondered whether float bowl level is low as bike stands for a long time between use and takes time to refill while cranking? Maybe need to mod tap to remove vacuum line?

Thanks for your thoughts.

[dandywarhol]

Were the valves checked for sealing when the big bore kit was fitted?

[Excalibre]

I had a bit of trouble setting the TPS after fitting my FCRs. Here's a quote from a previous post.

Regarding the TPS, I have a theory:

The TPS shaft on the FCR's is a spring-loaded arrangement, unlike the solid shaft on the original carbs.
It seemed to me that the FCR TPS shaft was prone to sticking a bit. I suspect that the process of fitting the TPS onto the shaft exacerbated the issue as the short shaft didn't seem to slide easily into the TPS, and I suspect that the assembly was pressing up against the carb body.

I found that when adjusting it, I'd get it right but if I tapped the TPS or carb body it'd go out of adjustment.

The answer....lubrication!

I smeared some light oil on the shaft so that it could slide easily and settle into place inside the TPS. I also squirted a small ammount of light oil (Innox)around where the shaft goes through the carb body. This seems to have solved the sticking problem.

Might be worth a try?

Cheers

[Killerwhale]

Killerwhale

Are you running with TPS removed and CDi mod? Can I expect some poor throttle response at the lower end as a result of permanent shift in ign timing? Seems there is mention of this in other TPS threads via search.

I actually used TPS at first as my FCR´s came with mounting for it, then it started acting up changing revs at standstill changing from neutral and first. Then modded the CDI and not noticable.
Now i have a TCIP4 igniter and use TPS again...

[misterdimwiddy]

Were the valves checked for sealing when the big bore kit was fitted?

Valves were removed and reground lightly when head and barrels came off for 878 install.

It flies and so I am confident that compression is good and valves not leaking. Saying that I did not do a fluid leak test before head went back on.

Eventually fired her up this morning with TPS still playing up. Took some starting using the accelerator pump (no airbox or trumpets) and scared the b'jesus out of the neighbours with some spectacular backfires. Now runs cleanly; tick over fine; throttle response is excellent..............and.........having checked mechanical connection to carbs, unplugged and reconnected TPS while running, this now seems to be behaving itself. No more rising to 3k back to zero.

Just got to replace all fuel tubes and possibly perishing inlet rubbers before dyno check.

Thanks everyone for your comment even if the symptoms have disappeared without a clear explanation.

Will post HP and ftlb plot when its been done.

Can't wait to ride it now and feel the difference.

Phil

[Killerwhale]

Were the valves checked for sealing when the big bore kit was fitted?

Thanks everyone for your comment even if the symptoms have disappeared without a clear explanation.

Phil

Check for oxidation on the connections, could be you scraped just enough when pulling it apart over and over...

[NWS870R]

I was about to suggest valves till i read your last post on the cold starting issue - if the inlet rubbers are perished change them. It also sounds like your fuel tap & (possibly?) vac pump could do with replacing? Hope this helps

[misterdimwiddy]

I was about to suggest valves till i read your last post on the cold starting issue - if the inlet rubbers are perished change them. It also sounds like your fuel tap & (possibly?) vac pump could do with replacing? Hope this helps

That's helpful thanks. My next move was going to be the fuel tap mod to remove the need for a vacuum line (search showed this with detail from Dixonj).

When you say vac pump I assume you mean the fuel pump? I have never messed with this but sounds like this also runs from a vac line? It has always been a reluctant starter when cold (since I got it 5 yrs ago) but fine when hot.

Do you know whether a repair/recon kit for the std fuel pump is available (pattern or Yamaha)?

Doesn't pop and bang on the over-run so I have never suspected the inlet rubbers to be leaking.

If my inlet rubbers are shot, this could have a combined effect on the tap function, fuel pump and starting (+ of course mixture) so more work yet to do. Relatively easy stuff though. I wonder whet Yamaha will fleece me for two small rubber mouldings?

I'll let you know what change I see with these mods.

[Mincehead]

M&P and Ebay UK now do the TRX vacuum fuel pump, they are readily available.