Hi!

I have a problem with my NSR 250 r sp-1990... It has the full HRC race kit.

New cylinders, top end rebuild kit and sparkplugs.

The problem: It wont start ; checked the spark; uneven and weak spark;
same problem at both spark plugs/coils.

When kickstarting without sparkplugs/ a "smacking"sound can be heard around the area where the ignitions coils and caps are located.

My guess is that the spark is leaking away somewhere between the ignition coils and sprakplugs.

Someone that know what is wrong or had the same problem?

Very happy for a answer!

Best regards!

If the HT lead (High tension - the bit going to the spark plug cap) or the cap are resting on any metal part of the engine, you will get an electrical arc from the lead / cap to the chassis.

Check the connectors going to the coils, as it is easy for the connectors to appear correctly fitted when it fact the spade has gone between the connector and the rubber boot.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

The terminals on the coils and also the connectors on the harness side can also corrode or oxidise, causing poor continuity to the coils. Check too, the LT wires/terminals at the PGM end.

The plug caps can also break down, and consider the fact that if they are original, they can be up to 18 years old now! Replace them with some decent silicone NGK caps.

Make sure the battery is 100%.

The spark can often appear weak, but may act very differently once the plug is back in the chamber and under compression. Testing for a spark with the plug out of the cylinder should be for that reason alone... testing for spark, not for quality of spark.
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Andy.
NSR-WORLD.COM

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As Andy says make sure the HRC rechargeable batterey has been left on the charger for the required hours before trying to start it.

The batteries don't last long so you may require another one anyway.
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If I have to take the carbs off once more...

Hi again!

Thanks for the rapid reply everyone!

The Battery is brand new..

I think I have solved the problem with poor spark; I discovered an old and
extremely rusty relay that i replaced with a new one; Now the spark is much
clearer and more even.

I will now try to start the engine and I will update this thread if it works or
not.

sorry for my bad english

Edit: Andy, do you have a part-number on those NGK silicone caps?

If you check the parts manual it shows 30720-KV3-771 as the part number for the genuine Honda one. You can take this to a Honda dealer and order it, or do it online at somewhere like www.lings.com - they're showing at 25 Euro's plus postage though!
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Yeah, that's about right, the NGK part number is TRS1408F, mine were somewhere around the £20 each + VAT mark from sparkplugs.co.uk.
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Yeyyy!

The engine fired up nicely after about 3 kicks!
I´ve been waiting for this to happen for 2 looong years!

Thanks for the Part numbers! It will be very useful!

By the way; Tyga Performance obviously sells the genuine Honda caps
for as little as 15.32 euro; 9 euro less than Lings

But i do not know if i should purcase stock caps or NGK caps?
Or if the stock sparkplugs fit into the NGK caps?

What do you guys think?

The NGK caps are a direct replacement for the Honda ones. The lower Honda one has a nice angle on it though, to point the HT lead back towards the frame spar where the coil is mounted. The NGK cap can leave the HT lead a little stretched if you trim it back at all (like you should) when you replace the cap.

I run the red NGK cap on the top, but an HRC "shorty" plug and cap on the bottom.
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Andy.
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Okay.

I have done a HRC head conversion as well, bur how do I get
the HRC shorty plug and cap...

I mean whats part number is it?

thanks

If you are using the genuine HRC heads then you can use the stock plugs. If you're using the '28 rear head swap as in the later SP manual then you will need to use the shorter plugs.

Honda part numbers for the shorty plugs are 31930-ND5-003 and 30700-ND5-751 for the caps
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If I have to take the carbs off once more...

OK then, as someone about to do the head conversion, what is the physical difference between the HRC and MC28 rear heads? A while ago, a well regarded member here stated emphatically that they were one and the same. I don't wish to stir up a hornets nest of trouble, just get it straight before I start the process.

Genuine HRC heads for the MC21 are the same shape as stock. Meaning the lower head still has a off set plug but differ with both volume and squish to the stock heads.

The MC28 HRC head swap is just using two stock rear heads. The heads are stockers and in no way HRC. The reason for this is when the '28 came out there where very few genuine HRC parts avaliable and as it was raced in SS/SP they were only allowed to use the stock heads.
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If I have to take the carbs off once more...

Think of it as "performing the HRC head conversion" as opposed to "fitting HRC heads".
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Andy.
NSR-WORLD.COM

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Thanks for the part numbers!

I,m using a mc28 rear heads on both cylinders and using stock spark plug.
It works just fine I think so why need shorty plug/cap?

By the way I´m using R cylinders with SP heads as HRC recommend for racing.
This to get a little more squish.