After my Winter layup and the fitting of the 300 kit, I heat cycled my 21 motor and it ran sweetly. Upon trying to ride on the road the bike had a pronounced flat spot at 4/5thou and would not rev beyond 10thou. If I shut the throttle and opened it quickly the motor would give a small backfire. I sent the bike in to Apex, they thought it could be a faulty coil. This was replaced along with a topend strip down and rebuild and a tweek to the carburation. The problem was still there! Jo suggested that it might be a faulty TPS or even the wiring harnesswas to blame. I have the bike back home now and am looking for any advise on TPS problems. I am "Green" when it comes to electrics. Is there any way of testing if my TPS is working as it should? If the bike is static things are ok, but once on the move"and jolting around" it is as if I have a loose connection somewhere. I have priced up a new TPS and they 'aint cheap. As an aside , I have unplugged and removed the three wires from the sidestand that clip into a conector under the seat area. (for athetic reasons) Please tell me that this is not the cause of my probs. The bike ran ok before with both wire splices "GPS and speed limiter". Any suggestion will be most welcome.
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Hmmmmm!

First thing I would suggest then is to return the wiring to a state where everything worked.

Next, the battery MUST be in 100% tip-top condition. I am sure Jo would have check this already, but (no disrespect to Apex) you must assume NOTHING!

Modifications should always be performed one at a time, and their performance (better or worse) then recorded. That way you can often narrow down a fault to a particular step you performed.

I can't imagine why the side-stand switch would be removed "for aesthetics". Not that it's necessarily going to be the cause of your misfire, but it is advisable to keep it as a safety feature. I'm sure many of us (myself included) have at some time ridden off with the stand down, only to come a cropper (or very nearly) on the first left-hander! The switch and associated wiring (I.M.O.) is hardly intrusive.

I think this thread could become very reminiscent of "nsrmonkey's" previous thread; read it here.

Andy.
NSR-WORLD.COM

I did my wire splice last year, and the bike ran ok then. I am not certain that the loom is causing me the promblem. Last night I undid and reconnected everything to do with the TPS and attempted to run the motor, it very reluctantly fired up, coughing and spluttering and backfiring.It only ran in tickover mode. If I attempted to open the throttle the engine "Swamped" and died. Is there any means of assertaining wether I am able to test the TPS for its working function? The TPS unit is very expensive and I would not like to purchase one only to find out that the problem lies elsewhere.
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Hmmmmm!

Sounds very much like the T.P.S., and very much like the symptoms Matt (TYGA) and I experienced on an MC28 motor fitted with RS250 carbs (no T.P.S. on the RS).

When an NSR sensor was fitted and turned to the correct setting, everything cleared up nicely!

Dave, PM me and I may be able to help you out with a set of carbs to "try".

Andy.
NSR-WORLD.COM

dave
not a clue what you guys are talking about with the t p s
but if andy cant help with the carbs i have a set you are more than welcome to try and cure the problem
so what and where is the t p s

Dave,

The reason it had a top end strip down was because a base gasket had been fitted on one cylinder and the old one not removed. Two gaskets were clearly visible, one of which had been doubled over and creased and it therefore had to be removed. On removing that top end we showed you the pictures of the incredibly poor finishing to the cylinders you had bought, along with the scuffing to the exhaust bridge which meant that the bike was very near to seizing. You stated that you did not want/could not afford to have the cylinders replated at this stage and to rebuild it as is.

On rebuilding the top end we reset the powervalves correctly.

We replaced the front coil because the top was broken and the wires inside were very corroded. This did improve the performance from how you delivered the bike to us, but did not cure it.

Then the battery was checked as this is always the first port of call on NSR's that run poorly. It was fine.

Following that we striped and inspected the carbs. Most of the breather tubes were either missing, or routed incorrectly, so these were fixed. The air screws had also been set totally wrongly so these was set correctly. Again, this improved things from how you delivered the bike to us, but did not cure it.

We explained to you that some of the problem was down to your airbox. This had random cutouts all over its top, as well as having all the internal crosswebbing removed by someone with a poor handling of a Stanley knife. At some point in its previous life it had been fitted incorrectly and the rubbers on it folded over. This now meant that it was hard to form a good seal with the carb mouths. For some reason it had also had the rubber bellmouths that protrude into the airbox also very crudely and badly removed. As a result of this the airflow that the carbs needed was being badly disturbed and the bike actually ran better with no airbox at all, than with the one you have. We therefore recommended that you replace it.

You have forgotten to mention that I told you the PGM has problems. We swapped it with one from a bike that has no problems and a number of other electrical problems that your bike has that you haven't mentioned were cured, although it made little difference to the running. Therefore, that also needs to be looked at as it is a known problem and may be causing others of an electrical and poor running nature.

As fas the wiring loom is concerned I told you that there are almost certainly problems with it. There were connectors in the middle of wires that should have been straight runs for no reasons whatsover, there were splices that appeared to have no function and in many cases wires with connectors and splices in them were exposed to the elements without any insulating tape round them. I explained that while on a stand the bike appeared to run fine most of the time, but that it intermittantly had problems. I pointed out the TPS in particular to you as being a potential problem as it was missing its inner shroud that keeps it firmly located, although given the state of the loom as a whole it would probably be better to replace it with a complete new one. I also explained to you that I could replace it if you wanted, but as cost was an issue you preferred to look at this area yourself.

Jo
Apex Leisure

Thanks to Nigel, I am now a little wiser, I fitted the carbs that he lent to me, but no joy, same probs as with my carbs. At least I now have eliminated the TPS from the equasion. Next quest to obtain a wiring harness fit it and ( fingers crossed) hope that my poorly NSR will be better.
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Hmmmmm!

Not teaching you to suck eggs old chap, but a wiring loom is a pretty simple piece of kit. There's nowt to it really that a multimeter won't find.

Might I suggest you get a wiring diagram and sit down for an afternoon of prodding? Wiggle whilst you test, and any loose connections should show up.

If you were closer I'd offer to help - my FJ is 19 years old and needs regular wiring tweaks to keep all the electrics working. In fact I neglected this a few years ago, and the main loom melted

I now check and clean connections every year!
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MC21SP Plaything
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