Single cylinder up to 4,000rpm

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vtryorks
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Single cylinder up to 4,000rpm

Post by vtryorks »

Well,

I kind of figured something wasnt right. It was just running very rough.

After being told some backfiring is normal, even the odd cough stall (by the good people here). I began to notice other things too. It was really struggling to pull at around 10mph in second. Clearly something was not right considering the torque of a VTR. It reminded me of riding the CBF500, which would make sense since if its only running on one cylinder, its about the same torque!

So I took it down for a once over by a local dealer. Two mechanics had a listen to it, seperately and told me that its only firing on one cylinder up to around 4,000rpm. So that probably explains it. I had noticed quite a surge in power from about 4k, but put this down to the power band of the bike, despite thinking previously that V2's pull roughly equally throughout the rev range.

Anyway, I've got it booked in next week, no way I'm going to tackle this myself. They suspect it might be electrical, so hopefully its nothing too serious.

Maybe once its sorted I'll finally get to ride a VTR as its supposed to ride. On the plus side, mechanic said the engines are bomb proof so whilst I am looking at the thick end of £300 to get all the work done that I wanted, at least I should end up with a solid machine at the end of it. :thumbup:

Annoying though.
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AMCQ46
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Re: Single cylinder up to 4,000rpm

Post by AMCQ46 »

that might explain why you thought it was such a handfull! and yes VTR has no real power band, that is why they are deceptivly fast.

lets hope you mechanic can find it, things like this can be tricky to diagnose.........did the bloke you bought it off mention this, I would be asking for some money off the sell price to cover the repair
AMcQ
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agentpineapple
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Re: Single cylinder up to 4,000rpm

Post by agentpineapple »

i'm with amcq on this one, i think i would be giving him a ring...............
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vtryorks
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Re: Single cylinder up to 4,000rpm

Post by vtryorks »

Nothing was mentioned in the auction terms about it having any form of fault. It was described as requiring a clean up.

I've never touched a Honda, or a twin, in my life, and even I knew that something wasnt right with it.

I will indeed be raising the matter with the seller. I cant really post any more about that aspect of things here, for obvious reasons.

Anyone have any pointers about what the issue might be? Could it be literally anything? Is it liable to be super expensive to sort out?

Cheers again guys.
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agentpineapple
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Re: Single cylinder up to 4,000rpm

Post by agentpineapple »

your best bet would be to ask tony mon, send him a p.m, he might be able to help.....
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darkember
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Re: Single cylinder up to 4,000rpm

Post by darkember »

Start with the basics, plugs, coils and work on from there.
tony.mon
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Re: Single cylinder up to 4,000rpm

Post by tony.mon »

Alright, let's get started with the basics....
If it's really only running on one up to 4, then running on 2 after that, you first need to find out if it will run on 2 at tickover.
If started from cold, carefully touch each exhaust to feel if one gets hot and the other doesn't.

Assuming it will tickover on 2, then it will probably be a carb or fuelling issue.

If it will only fire on one cylinder at tickover, then it may be an electrical (ignition? coils? ECU? problem, or just maybe it is low on compression.
This can be caused by a poor rebuild when the CCT has failed, knackered valve seats, or if it's the front cylinder at fault, possibly a worn cylinder- I have an engine with that fault in the garage right now.

I would also check the plug cap, plug and high tension leads- all can (with a bit of playing around) be swapped from one end to the other to see if the problem also moves across....

Otherwise the culprit is likely to be fuel related, choke sticking on, fuel tap problem, carb diaphragm, etc, etc.

You just have to work through the checklist......
It's not falling off, it's an upgrade opportunity.
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benny hedges
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Re: Single cylinder up to 4,000rpm

Post by benny hedges »

tony.mon wrote:Alright, let's get started with the basics....
the culprit is likely to be fuel related, choke sticking on, fuel tap problem, carb diaphragm, etc, etc.

You just have to work through the checklist......
possible blocked pilot jet... the small one at the side of the main jet.
the hole in the centre is only .45mm then you have the even smaller emulsion drillings in the sides... if any debris has got through the pilot jet will always catch it first.
if this is the case it's well worth fitting a clear fuel filter for at least a few tankfulls as you dont want to be clearing it out again,

how old are the plugs btw.... if they are old iridium plugs the gap is probably massive... the front cyl plug on mine had a gap of like 1.5mm and was very spluttery at low rpm

*when tony says touch each exhaust.. he means the header from the cylinder, and not the cans
obviously be carefull as they get very hot very quickly!
You do not have to say anything. But it may harm your defence if you do not mention when posting something which you later rely on in quote. Anything you do say may be ripped to sh*t.
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vtryorks
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Re: Single cylinder up to 4,000rpm

Post by vtryorks »

I'll give this a bash just to try and help the dealer. Thanks guys.

The place I'm taking it to is a Honda main dealer and the chap told me their chief mechanic will look at it. They have been in business for many years, well, its Castle Motorcycles.

Benny, you're reasonably local, their reputation seems good as far as I know?

Thanks again everyone, I really am grateful for all the help.
tony.mon
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Re: Single cylinder up to 4,000rpm

Post by tony.mon »

Just to check, it runs roughly up to 4000 and then it's ok to the redline?

Because I see you have manuals fitted, and one of the things that can go wrong in that process is to get the valve timing out on one cylinder by 180 degrees.

If that's been done, the symptoms are that the bike runs fine up to about 4-5000 rpm and then gets breathless, and won't pull to the redline in gear- feels like it's running on one cylinder (which effectively it is, as over those revs the airbox can't fill quickly enough and only one cylinder gets enough air) .

It's the opposite of what you're describing, but thought I'd check....
It's not falling off, it's an upgrade opportunity.
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vtryorks
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Re: Single cylinder up to 4,000rpm

Post by vtryorks »

Hi Tony,

I've got stop modded CCT's on it, not sure if that makes a difference.

The bike does pull after 4k rpm but honestly, I have not red lined it yet so I dont really know although I suspect it would pull, I've had only split second loses of power.
qfo
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Re: Single cylinder up to 4,000rpm

Post by qfo »

What does Tickover mean?
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AMCQ46
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Re: Single cylinder up to 4,000rpm

Post by AMCQ46 »

qfo wrote:What does Tickover mean?
idle speed
AMcQ
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benny hedges
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Re: Single cylinder up to 4,000rpm

Post by benny hedges »

tony.mon wrote:
It's the opposite of what you're describing, but thought I'd check....
maybe he's timed it 360 degrees out! :Beer Popcorn:
You do not have to say anything. But it may harm your defence if you do not mention when posting something which you later rely on in quote. Anything you do say may be ripped to sh*t.
tony.mon
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Re: Single cylinder up to 4,000rpm

Post by tony.mon »

If what you are now saying is that the bike ISN'T only running on one cylinder, but runs on two with an occasional misfire on one cylinder....This sounds like the airbox cough.......
Which is where you feel (through your nuts, if you sit close to the tank) a muffled bang under the tank, usually at or just above tickover speed.

Balancing carbs helps, turning tickover up to 1350 helps, but they all do it occasionally.

It's because they are large carbs and don't work very well at low air flows.

Please describe the misfire better, is it continuous, only when cold, worse at the start of a ride, does it under load as well as when in neutral, whether it misses a beat or cuts out for a while, how long a while is, etc, etc.
It's not falling off, it's an upgrade opportunity.
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