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I ride like I mean it
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Discussion Starter · #1 ·
yesterday morning my 99' r6 was chugging horribly in 1st and 2nd. I had hoped it was just a bad bit of petrol, and after five minutes of riding, the problem vanished. However, whilst it was fine on the trip home from work, this morning I found exactly the same problem. Chugging, as if not enough fuel was getting through to the furnace.

My mechanically minded mate at work said it was a carb problem. Advised me to first try draining the bowls. If that did not cure the issue then to strip the carbs down and clean them, which would probably require a day of work.

Having read the guide to clean the carbs, I am left, still concluding that it is a step or five beyond my expertise. I have not the space nor the confidence to attempt such a thing. Either thing.

Especially given the carbs will need resynching after I have cleaned them, that is, if I can even get to them. Lifting the tank reveals absolute chaos to my eyes.

Is this a job I should take to my trusted mechanic? Is there a far more simple remedy I can first try, such as a fuel additive?

Does this chugging for five minutes seem definitely a carb issue?

any advice is welcome.

cheers,
tgp
 

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Mr. HER6
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2,084 Posts
Yes, sounds like there's some minor blockage of fuel. The engine needs a bit of extra fuel when it's cold, so it makes sense that the issue gets better once things have heated up. I think this is something worth tackling yourself. It's really not that scary. Follow the manual as you work, and things will make sense and of course you can come here for more advise. Plus I'm still amazed at how often I hear of people taking their bikes to mechanics who aren't capable of sorting out the carbs.

Also, there's no need to separate the carbs at this point. Personally, I have never needed to separate a set. Leave the whole bank together and they will stay in sync. 1st step, locate the fuel screws (parts diagram calls them the pilot screw set) and see what their current setting is. May not match the book, but if everything is stock it should. Completely remove them along with the pilot jets and main jets. See if you can find any blockages, and give them a good cleaning in carb cleaner. Let them soak in it for a day or two if possible. Spray carb cleaner into the passages they came out of and let that soak as well. Inspect the needle valve tips that are attached to the floats for wear, and measure and adjust the float height.

That's the basics of sorting them out. Generally, when older bikes start running rough, they just have some buildup starting to clog those tiny passages, and they are so small that it has a significant impact on the fuel flow.
 

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I ride like I mean it
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92 Posts
Discussion Starter · #3 ·
Cheers for the response, mate. It certainly removed some of my apprehension to learn that I need not resync and take the things completely apart.

I took the bike out this morning and then again this evening and it was absolutely perfect. So perhaps I need not delve into the carbs?

They were resynched a few months back by a mechanic I trust, who told me he found some oil in the carbs, so I assume he would have checked them for build-up of grime or whatever else can build up there.

I will hope that all is fine and dandy.
 

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I ride like I mean it
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92 Posts
Discussion Starter · #4 ·
Yes, sounds like there's some minor blockage of fuel. The engine needs a bit of extra fuel when it's cold, so it makes sense that the issue gets better once things have heated up. I think this is something worth tackling yourself. It's really not that scary. Follow the manual as you work, and things will make sense and of course you can come here for more advise. Plus I'm still amazed at how often I hear of people taking their bikes to mechanics who aren't capable of sorting out the carbs.

Also, there's no need to separate the carbs at this point. Personally, I have never needed to separate a set. Leave the whole bank together and they will stay in sync. 1st step, locate the fuel screws (parts diagram calls them the pilot screw set) and see what their current setting is. May not match the book, but if everything is stock it should. Completely remove them along with the pilot jets and main jets. See if you can find any blockages, and give them a good cleaning in carb cleaner. Let them soak in it for a day or two if possible. Spray carb cleaner into the passages they came out of and let that soak as well. Inspect the needle valve tips that are attached to the floats for wear, and measure and adjust the float height.

That's the basics of sorting them out. Generally, when older bikes start running rough, they just have some buildup starting to clog those tiny passages, and they are so small that it has a significant impact on the fuel flow.
I had a mechanic advise me that my carbs sounded 'fluffy' earlier this year. I thought fine, sync them for me please whilst changing my spark plugs. They returned the bike with the revs hanging horridly. three times I returned, the last of which i was told that whoever last synced the carbs had not aligned the air screws (it was THEM!). Also that the carbs were perfectly synced, so it must be the manifold or carbs causing the hanging revs. They explained that I did not have the problem before the service because only by syncing the carbs was the problem unearthed...which made no sense to me.

I took the bike to another mechanic who was appalled at the state of my carbs. He showed me printouts of them all out of line horribly. Also a picture of them all in line after his work. There was also some oil in the carbs (perhaps from my overspraying of oil on the air filter I installed prior to any service). Lastly, the other mechanics had not replaced two of the screws in the airbox casing.

Whilst he was content with the carbs now, his gadget also showed valve opening information and he told me the engine was basically a bit ****ed. It had probably been raced in the past and to remedy the problem would cost likely as much as the bike was worth! Still, he said the bike remained a weaopn, just an old whore of a weapon.

Since then, I changed oil, oil filter, cleaned the chain and sprockets, new battery and it has been running superbly until last week.

Whilst it was fine over the weekend, I noticed the same problem yesterday, after a lengthy ride, stopped for half hour then the same wretched chugging at low revs in 1st and 2nd. It vanished after five minutes of riding. And again today, during the first few minutes of my ride home from work.

Does this mean deifnitely the carbs need attention? And I cannot hope the problem simply vanishes in time?

Taking the whole thing out seems less worriesome...but adjusting the float once more strikes me as fiddly and something I could easily **** up?

If I am to take it to the triusted mechanic, how many hours work would it be to do the carb cleaning routine?
 

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Mr. HER6
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See! Some of these guys have no business touching carburetors. At least you found a guy who seems to know what he's doing.

I assume the bit about valve opening means he checked the valve clearances (also called lash). Obviously it won't run tip-top if it's out of spec, but if it's bad enough it could be contributing to your issues. The measurement is the gap between the cam lobe and bucket on the end of the valve. That gap gets smaller over time, and eventually it can prevent the valve from completely closing and causing a loss of compression as the air can escape. Did he give you the details of those measurements? Or maybe he did a compression or leak-down test. If he found that compression is low and it's due to the piston rings, then yea, it's often not worth fixing unless you can do the work yourself. Find out exactly what he checked and found.

The problem definitely won't cure itself. Could be the carbs, the valves, or both. Prices for a proper cleaning and adjustment seem to vary a lot. Likely in the $300-$400 range, but you'll just have to ask your guy. But if you've got valve clearance issues you'll have to adjust that to get it running right.
 

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My R6 eats Ninjas.
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I had a mechanic advise me that my carbs sounded 'fluffy' earlier this year. I thought fine, sync them for me please whilst changing my spark plugs. They returned the bike with the revs hanging horridly. three times I returned, the last of which i was told that whoever last synced the carbs had not aligned the air screws (it was THEM!). Also that the carbs were perfectly synced, so it must be the manifold or carbs causing the hanging revs. They explained that I did not have the problem before the service because only by syncing the carbs was the problem unearthed...which made no sense to me.

I took the bike to another mechanic who was appalled at the state of my carbs. He showed me printouts of them all out of line horribly. Also a picture of them all in line after his work. There was also some oil in the carbs (perhaps from my overspraying of oil on the air filter I installed prior to any service). Lastly, the other mechanics had not replaced two of the screws in the airbox casing.

Whilst he was content with the carbs now, his gadget also showed valve opening information and he told me the engine was basically a bit ****ed. It had probably been raced in the past and to remedy the problem would cost likely as much as the bike was worth! Still, he said the bike remained a weaopn, just an old whore of a weapon.

Since then, I changed oil, oil filter, cleaned the chain and sprockets, new battery and it has been running superbly until last week.

Whilst it was fine over the weekend, I noticed the same problem yesterday, after a lengthy ride, stopped for half hour then the same wretched chugging at low revs in 1st and 2nd. It vanished after five minutes of riding. And again today, during the first few minutes of my ride home from work.

Does this mean deifnitely the carbs need attention? And I cannot hope the problem simply vanishes in time?

Taking the whole thing out seems less worriesome...but adjusting the float once more strikes me as fiddly and something I could easily **** up?

If I am to take it to the triusted mechanic, how many hours work would it be to do the carb cleaning routine?
If there is excess air getting into the airbox from a leak, the air/fuel ratio will be thrown off and cause the bike to bog down since there is more air and the engine is starving for fuel. To check this you can pull out your spark plugs and check the tips to see what colors they are.
Black = too rich
Tan = perfect A/F ratio
White = Lean

Also the chugging at low revs or idle indicates the pilot jets may be plugged up. This is a normal fault of carbs, and usually requires them to be taken out and cleaned by hand. To do so, you can take some thin copper wire, and clean the jets out and all the openings which fuel comes out of. Be careful removing the jets as they are brass and very soft metal. Using copper wire won't harm the jets as it is softer than brass, but other types of wires may scratch the brass jets, so make sure you use copper. Cleaning the carbs is not that bad, removing them from the bike and installing them is the tougher part of the job.
 

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I ride like I mean it
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92 Posts
Discussion Starter · #8 ·
the screws were replaced...so no extra air getting in from the airbox.

I fail to understand why the chugging at low revs is magically fixed after 5 minutes or so of riding, and the quicker I find the high revs, the quicker the problem vanishes.

I shall continue to try locate the mechanic, otherwise, I will be forced to attempt the carb cleaning myself...if a carb issue seems the most obvious problem?
 

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Mr. HER6
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2,084 Posts
What do you mean by leakage? What was leaking? How bad? Got any numbers? If you've got a compression problem you can't overcome that by fiddling with the carbs. At best, you might be able to mask it a bit.

As the engine warms up the effective fuel mixture naturally richens. That's why you need the choke to start when it's cold. So if it is running bad because of fuel restriction, a hot engine will help. Also, you have to remember there are different regimes under which the carbs meter fuel out. At idle and just off idle, obviously requires the least amount of fuel. The pilot jet and fuel screw dictate the amount of fuel to flow under that regime and since they have the smallest passages they are likely the first ones to suffer from buildup. At larger throttle positions and higher rpm the other fuel control circuit takes over and overshadows the pilot circuit, masking problems it may be having.
 

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I ride like I mean it
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92 Posts
Discussion Starter · #10 ·
Thanks again for the education, HO!

The leakage was due to valves not closing fully ( I vaguely recall!), with the work to correct probably reaching past the sale value of the bike. All I was interested in was that the engine was safe and the carbs has been properly synced. The hanging revs were solely due to misadjusted carbs.

This morning the bike was perfect, no problem whatsoever. I wonder why it is so intermittent?

Having a tough job getting hold of the mechanic I trust, so may delve myself this weekend, depends how easy it is to get the things out and also what the likely problem is. Hard to diagnose from afar I know...but does it seem like an issue with jets?
 

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Mr. HER6
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2,084 Posts
If that's the case your results may be limited.

I would focus on the pilot jet and fuel screws. You can even experiment with the settings. Say, turn the fuel screws 1/4 turn out (richer) and see how it goes for a few days. Then try another 1/4 turn. Keep tabs on where you started and what you changed so you can quickly go back if it gets a lot worse.
 

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I ride like I mean it
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92 Posts
Discussion Starter · #12 ·
If that's the case your results may be limited.

I would focus on the pilot jet and fuel screws. You can even experiment with the settings. Say, turn the fuel screws 1/4 turn out (richer) and see how it goes for a few days. Then try another 1/4 turn. Keep tabs on where you started and what you changed so you can quickly go back if it gets a lot worse.
Well, morning was fine for the 25 minute ride to work and the ride home also without any issue whatsoever. False hope that the problem may have vanished?
 

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I ride like I mean it
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92 Posts
Discussion Starter · #13 ·
It has been fine for the last few days now, so I am hoping the problem has vanished!

Yet I have been pondering the words of the mechanic from a few month back. I will visit him tomorrow and try get some details of what he had tried to explain.

A friend at work suggested that I give his mate's a try...they specialize in cylinder head reconditioning. valve seat inserting and more. I have no idea how much the job would cost, nor even yet what the job could be! Yet I am aware that my bike, 68k on the clock, a fair few scratches from previous scrapes, would only fetch maybe $2-2500AU? For me to grab a second hand 600 alternative or bigger would require probably that much again. If I can pay...$1-1500 for the valves to be repaired (is this part of an engine rebuild? and that would greatly improve the engine, cure the not fully closing valve problem and add life of at least a few more years to the bike...I would gladly spend the money, because old as the old whore may be, I love the bike! Regardless of its age, and condition, it remains so damn violently swift from the off. Perhaps I just ride fast, but I think its the finest acceleration I have found on a bike, as well as the most agile. I greatly enjoyed the cbr600f I had in england, yet it was smoother, the power delivery less berserker.

Am I miles out of the probable pricing for fixing the valves?
 
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