Blocked main jet perhaps?

that should show the dyno print out

the prick!!!

So..that is a full power run and it looks to fuel pretty nice...but is poorly.

I do recall that we had a chap on here, Hamster, who had his NC30 dyno'd. It made less than 50 bhp and he swore that this was fine.

I get the feeling that something needs looking at on this bike.

Engines are simple beasts... you compress some air/fuel mix and the more you can compress and ignite, the more power you have.

This graph shows that the bike is not even revving out. It should still be producing power into 13k revs. Yours is dropping off at 11.5.


That is a shit quality graph, but you can see the curve - smooth and climbs all the way to a peak at 13750.

In my experience, electrical faults usually are very obvious. They work, or they don't.

You are missing a qtr of your power...but a cylinder missing spark would probably give a very rich A/F ratio as there is a lot of unburned fuel in the system. You would hear it too.

So, if all else sounds right, fuels right and has been checked...It leaves little to go on.

You have air, you have fuel and all you need then is compression and a spark.

So, I'd check the spark plugs look the healthy tan colour they should for that A/F mix - if one is black, you have the winner! Swap it..

Or, failing that, compression test.

Cheers for that cmsmj1 but the guys in the shop swear that everything mechanical is going good , compresion and spark included, dont know what the story is but ill let yis know if I get it sorted.

its being starved of fuel between 5-8k rpm. the drop in power is matched by a lean fuel/air mix between these points. id strip and clean/rebuild your carbs and mod the fuel tap as per HRC.

peavey wrote:Cheers for that cmsmj1 but the guys in the shop swear that everything mechanical is going good , compresion and spark included, dont know what the story is but ill let yis know if I get it sorted.

I'd be convinced if it was running through treacle and your chain was made of rusty siezied links with a side order of failed wheel bearings and brake drag thrown in.

What about these things? It is not right..the guys in the shop need to produce the compression results to you..but I bet a good fiver that they never tested it as it needs an 8mm adaptor and not many people have one!

The bike is poorly..

@ Mo - how do you explain peak power at only 11k revs and it won't rev out? Is it breaking down under load?

@ Peavey - have you checked the earths and HT leads - clean and solid connections? Plugs - what colour are the tips?

mo haggs wrote:its being starved of fuel between 5-8k rpm. the drop in power is matched by a lean fuel/air mix between these points. id strip and clean/rebuild your carbs and mod the fuel tap as per HRC.

What's the fuel tap mod?

yazza54 wrote:

mo haggs wrote:its being starved of fuel between 5-8k rpm. the drop in power is matched by a lean fuel/air mix between these points. id strip and clean/rebuild your carbs and mod the fuel tap as per HRC.

What's the fuel tap mod?

Someting that most people say is not worth the risk of having your sump filled with petrol...and it will happen, sometime!

it removes the vacuum operation from the tap so it is always on..

Only useful, IMO, for race bikes (and my race bike does not run it either..)