Firestorm running rough

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Firestorm running rough

My 97 Firestorm has been running only on the front cylinder lately. I have put 2 new plugs in and checked the sparks on both cylinders - OK

I am thinking the culprit could be the petrol tap and the fuel supply. Is there a simple test I can do to check it's ok. Is it a common fault?

Also, Iam thinking it could be the float chamber in the rear carb. I don't relish the thought of taking then off. Again, can any pre checks be done on carbs.

Thanks in advance


Before you attack the fuel system it's worth double checking the ignition - it's quite possible for a weak ignition system to give a spark with the plug out, but not when in a closed combustion chamber full of compressed gas. Beg/borrow/buy a timing strobe and trigger it off the front pot. If it's triggering OK then you know you're still getting a spark with the plug in there. If not, then it's most likely HT cap, HT lead, coil, possibly wiring TO the coil.If it's not ignition then it's compression or fuel. So checking the compression can be a good idea too - especially if the problem came on fairly suddenly, or is worse when cold.Petrol tap and fuel supply won't cause bad running on only one cylinder. How sure are you that the problem is on the front only? Check by feeling (carefully) the temperatures of the exhaust header pipes, and also by checking the colours of the spark plugs. Do you still have the ones you replaced?If it's definitely only on one, and you've ruled out the other stuff, then it's a problem with the carb or injection on that cylinder, or possibly an air leak, tho' I'd expect an air leak to only cause problems at lower speeds / loads.Air leaks are easy to diagnose tho' by spraying a little carb cleaner around the inlet stubs with the engine running - if the engine picks up or slow down then you know there's a leak letting some of the "extra fuel" in. Carbs-wise, what to look for really depends on what the symptoms are. You can usually check the fuel float level without removing them by using some clear PVC hose onto the float bowl drain and opening it with the petrol tap on "pri" - the fuel will rise  to the same level as in the float bowl so if there's too little or too much then that might be a problem. Other than that I can't think of any carb problems that would give you NO running on one cylinder. The cold-start valve sticking on would cause poor running once it's been running for a few minutes and getting up to temperature, or poor starting if it's stuck off.If it's injection then a dodgy plug onto the injector is most likely, or a failed injector. But you'd expect to see the FI light come on somewhere.

Thanks for helpful reply. This has given me some useful ideas to try.Let me just explain the problem in more detail. Maybe it will assist you or anyone else in the know to diagnose.It is the rear cylinder that does not fire. I place my hand on the rear header pipe and it is not getting warm.If I pull out the choke the engine will run a little better and sometimes on both cylinders. If I push in the choke the engine will either:1) Die2) Revert back to being a singleOccasionally, when I start the engine cold it will run as normal for about 2/3 minutes before reverting back to a single.If I open the throttle about 1/4 it dies.I have removed the tank and used a syringe to constantly top up the end of the fuel pipes with the engine running. It ticks over on both cylinders but will not rev out beyond 1/4 throttle.I have removed, checked and cleaned up the slide from the rear carb. All seems to be well.Other than change the plugs I have not checked any other electrical gear on the bike.I want to now check the coils/ignition unit. How best can I do that?Is it a siple continuity/resistance check?Any ideas appreciatedCheersMike

Problem solved! On the petrol tap there are two large connections for the fuel pipes and two other, small connections, one for vac and one for drain. I had the vac pipe connected to the drain DOH!!!The bike starts up and ticks over nicely now

I'm having the same problem with my 98" vtr1000, I've taken my carbs apart numerous times within the last week only to realize that the front header is not getting nearly as got as the rear one not nearly as quick either. I have cleaned and lubricated the choke assembly with wd40, checked for spark on both cylinders, and they both spark like crazy... When taking apart the carbs, I've noticed fuel in both floats... Any clues? There are two skinny tubes under the gas tank, I'm thinking maybe they got reversed in the process? So I'll pose the question, the tube with the filter (or that's what it looks like) does that connect behind the petcock or does that connect to the bottom of the tank where the fat black tube connects to the nipple where there are two male connectors? A picture of what the bottom of the tank properly hooked up would be very helpful...

Thanks a bunch.

If there's fuel in both carbs then the problem is unlikely to be fuel supply. Crucially, you don't need to take the carbs apart to check - the drain screws at the bottom of the float bowls allow you to check fuel level in the float bowl by making a simple manometer with a piece of clear hose. If you don't understand how, then ask. But since there appears to fuel in both  let's assume that the problem isn't actually fuelling. To shed a little more light on it, can you say how long the problem has been going on, under what conditions it started, did it coincide with anything else? Does it improve with revs or get worse? Does it improve with the choke on or get worse? A key point to note is that just because a spark plug sparks OK outside the cylinder, it doesn't mean it will do when it's in a cylinder of hot, fuel-loaded compressed air - that's a much harder job. To check, you need to use a timing strobe. With the spark plug correctly tightened into the cylinder and everything connected up, the HT lead should trigger the strobe when the engine is turning over / running. If not then there's a problem. Even if it does it could still be a problem in the HT cap or spark-plug. Both are relatively cheap to replace, and both suffer most on the front cylinder. It could also be a compression problem. To check that without stripping the engine you need a compression tester.

I'm having a similar problem. I just bought the bike knowing there was a small oil leak I rode the bike with the leak just once, it ran spot on. Then I set about sorting the leak. To do this I removed the carbs, the leak turned out to be a loose bolt on the engine. Tightened and the leak has stopped. However the bike ran absolutely appaling as if it had only one cylinder. After reading the above posts I realised the vac pipe on the fuel tap was connected to the drain, I have to say at this point I didn't realise this straight away and ran the bike a good few miles with the pipes connected wrongly every time with really bad running. I then changed the pipes and it now runs a lot better however it is still incredibly lumpy in low Revs then it will run for a few miles fine then when I want power it then dies on me, this happens around 4 to 5000 revs. Once the bike comes to a halt, it won't start while I'm rolling along, it starts fine then does exactly the same thing after a mile or 2. Im beginning to wonder if I have damaged anything running the vac pipe connected wrongly.
The bike will start and tick over fine. Anybody have any ideas nothing was done to the carbs apart from being lifted of and then put back on in fact they weren't even taken completly of the bike, this is doing my head in I need my bike fixed

Three prime suspects :- 1/. Main jet blocked 2/. HT lead earthing or bad insulation 3/. Already said, air leak on the intake side There are plenty more but I'd look at these first, see if you can give a bit more detail.

I will check these out as soon as I get a chance thanks. As for other details I have changed the spark plugs but the problem never got any better. I don't have any specialist tools how would you go about checking for an air leak or a jet blocked? Are these quite simple to check for?
What other details would help to narrow it down mate? It's a 2001 bike it's the first twin I have ridden so can't compare it to anything I have had before. The first time I rode it it was great pulled like a train not lumpy at all. It's just had its cam chain tensioners done the end of last year and by all accounts it hasn't been run much since. Thought it sounded very tappy but thought that was the tensioners. Im not very mechanical I just like the bike. Just needing it running like it was.

Just read the last posts again I will get some carb cleaner tomorrow to check for air leaks, any advice on how to check out the other suspects would be appreciated.

Hi Vic,           Safer than carb cleaner, especially on a hot engine is a butane torch, turn it on, don't light of course and run it slowly round all intakes, revs will rise if leak. Is it possible to swap HT leads or borrow one? Try making sure the lead is cleaned off and check for cracking. Carbs I'm afraid will need to be stripped and cleaned (blown through) if blocked. First thing is to logically narrow down the fault, and this applies to any fault, there are 3 requirements to run any engine, fuel, ignition source and compression. Take them one by one with ignition being the most likely and easiest to check, fuel 2nd and compression 3rd. So do all checks we've said on ignition side, then check fuel is getting from tank to carbs and from carbs to cylinder. Do the last bit by removing the plug letting cylinder completely dry out, putting plug in but do not connect HT leads, spin engine over and completely remove plug - is it wet and can you smell fuel. A bit simplistic but good enough indicator for now, see what you get.

Cheers man that gives me something to work on I will keep this thread posted on any results good or bad.
Cheers again

OK Vic, this has me a bit worried can you explain a bit more? 'It's just had its cam chain tensioners done the end of last year and by all accounts it hasn't been run much since', What was it running like after change?, are they manual? and what do you mean 'by all accounts?' is it not just you riding it?

I just bought the bike a week ago mate. The cam tensioners are manual now. This was carried out in August last year according to the receipt. There is no mileage on the receipt but going by old mot's the mileage has only went up 2000 miles in the last 4 years. The guy I bought it off collected bikes and rarely rode them, obviously this is what he told me but I have no reason not to believe him. According to him the bike was rode home after the tensioners were done and hasn't moved a wheel since. Now I would bring it back to the garage where the work was done but it's 300 mile away, I stay in Scotland and I travelled and got the bike from Manchester area. When I did buy it the test run was fine a bit tappity but it wasn't lumpy and really pulled. I got it home and had a decent run on it and again no problems at all apart from the slight oil leak which I knew was there. Unfortunately to get to where the leak was a mate of mine took the carbs of. He didn't pay attention to where the vac pipe went hence the problems at first. I finally took the tap off the tank and figured out the vac pipe was in the wrong place. Thinking that was the problem sorted went out on a run. It was lumpy low Revs and after a mile or 2 I opened it up sometimes with no issues apart from being lumpy but more often than not would get to around 5000 Revs then get really lumpy and lurchy then it would just die. This is were I have no hair left as I have pulled it all out trying to sort it.

By the way a tip to all you guys as the same mistake in mixing up pipes seems to be happening. Buy a paint marking pen, better still two or three colours, then before dismantling put a little blob on pipe and on part it connects to, dries in seconds. Then, especially if you leave it dismantled a while, you can never ever reassemble incorrectly, works a treat, same for wiring connectors.  

Ok quick update. Took the tank back off just to check the fuel tap is working correctly which it is however when I took the 2 fuel pipes of the one going to the rear cylinder was bone dry, the other had the remnants of fuel in it. I then undid the drain screw for that side of the carbs just to see if there was fuel in it which there was. Can't run the bike up the weather is absolutely rubbish to be standing outside working on a bike. Any thoughts on the dry fuel pipe would be appreciated

It's very quiet???

Had enough of trying to find what's wrong with the bike put it in to the garage yesterday. They stripped the carbs down and found nothing wrong which is not great but there you go. They are going to start on the electrics tomorrow. ..I can feel a big bill coming my way..oh the joys of bikes !!

Ok bike is back running sweet as.....

The garage sorted the carbs and in the end that's what it was. Collected it today and went for a good run it never missed a beat.

The garage found grit in the carb bowl. They said it wasn't anything too great but I think the whole stripping the carbs down then a rebuild and balance has just done it. So I'm a bit lighter in the old wallet but at least the bike is running now, so we'll pleased. Let's just hope that's it for a while.

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