Engine not revving properly

[Angus]

I recently finished putting together a H1F. The bike was bought as an unfinished restoration. The engine had been rebuilt as had the carburettors and a new electronic ignition was supplied.
My problem is that the bike won’t rev above 3500 revs when you’re riding it but will rev right round to the red when in neutral at a standstill.
Has anyone got any suggestions as to what it could be ?
Thanks in anticipation Angus

[Nigel S]

Firstly, what was used for the carb rebuild, Mikuni or Keyster ?

When the engine is not under load I.E Standing still it will always rev to the limit. Once the engine is under load I.E on the road if it's not getting enough fuel, air or mixture of both. Or if the exhausts are clogged. It will not run properly.
If you are running standard air box and exhausts ensure both are free from blockages. If carbs rebuilt with Keyster parts, rebuild with correct Mikuni parts (suggest Steve at Motocarb).

On the down side if this is all clear check that no weekend warrior has butchered you barrels and heads.

Let me know how it goes.

[Pierrot974]

Hi.
You say you have a new ignition, original or aftermarket ?
I couldn't go over 5000 rpm when I fitted a Powerdynamo on my H1A.

[mraxl]

RPM can be limited if regulator is bad.

[Doctorpayday]

Hi

Had similar, proved to be mouse nests in 2 of the 3 pipes.

Rodent free and ran without a squeak.

Doc

[skub]

Hi

Had similar, proved to be mouse nests in 2 of the 3 pipes.

Rodent free and ran without a squeak.

Doc

Not even a whiskered plug?

[Angus]

Hi everyone, sorry for the delay but I’ve been away.
Thanks for all the feedback. This is how things are at the moment. I’ve got mikuni carbs fitted and standard air filter all new parts. The exhausts are higgspeed again new ones so I can rule out danger mouse squatting anywhere.
I did remove all the carbs and checked the float heights. All done from information off the club as I’ve never done it before. The float height was just over 25mm and I reset them to 23mm but it still wouldn’t rev. Unfortunately I didn’t check what parts had been used by whoever rebuilt them so I need to remove them again to check. The new electronic ignition is a Lakeland stockbox combo unit. Is there a way I can check the regulator out to see if that is working properly ?
Again , many thanks for your help. I’ll let you know how things are when I’ve checked the carbs out again
Cheers-Angus

[Wolfie]

As with most of the above replies, Either fuel or air restriction is by far the most likely cause (incorrect fuel / air mixture), with Electrickery things lagging well behind as a cause.

Checking the regulator is best done on the bike, simple test is to let it tick over for a while with the headlight on and see if the light brightens when revved.
A more accurate test is to put a meter across the battery and measure around 14.5V when revved.

[Angus]

Hi.
This is how I stand now with my H1F not revving above 3500. I put a volt meter across the battery with the engine running and got just over 15v so I’m guessing this is ok.
I’ve removed the left hand carb and stripped down. The main jet has got 100 on it but can’t see the square in square logo which I understand means it is a mikuni part. The pilot jet has got 30 on it and matches the picture on the club information site saying that it’s the correct one. The needle jet has got 172- 0.4 and the mikuni logo.
As far as I can see these are ok. I haven’t checked the other 2 carbs as they was all rebuilt by the same person so I’m guessing they’re ok. I can remove and check them if anyone thinks it should be done.
Any suggestions would be greatly appreciated as I’m currently scratching my head and other bits.it probably doesn’t help that I’ve never had a Kawasaki triple before
Cheers-Angus

[TallyB]

Have you checked your filter yet? Might be worth taking it out and having a quick run around the block.

[Angus]

It is a new filter but it probably is worth taking it out and then trying the bike out. Are the air screws critical on the carbs ? I’ve set these at 1 1/4 turns out
Angus

[Wolfie]

Genuine Mikuni parts have the "square" logo, so it looks like your main jets aren't Mikuni original parts. Best to replace them since they are unknown.

Airscrews set the Mixture at tickover and low throttle openings (#1) so unlikely to make any contribution to your problem, just set them as per the book or close for now.

#1 The Pilot Jet / Airscrew set the mixture for Low throttle openings however they can still have a (much reduced) effect for higher openings, since your problem appears at high revs/openings it's unlikely to be the cause. Although they may need some adjustment once the main problem is bottomed.

There is a lot of good information on MrAxl.. Triples Resources. https://www.kawatriple.com/carbtuning.htm

[Angus]

Thanks. I’ll get some new main jets and see how it goes

[Triple Parts]

You can try, but I doubt very much that the main jets will cause the symptoms you describe. They would have to be massively out of spec and it would still rev out on part throttle in the lower gears.

[h2al]

Have you got the standard funnel fitted to the airbox..? If so, is it fitted correctly...? Make sure it's not being trapped/squashed when you shut the seat.

[Angus]

Thanks for the suggestions. I’ll fit the new main jets when they arrive and follow the other suggestions. I’ll post the results when I find out how it goes