Intermittent Front Cylinder
07-09-2017, 12:59 PM
#1
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Intermittent Front Cylinder
2000 Superhawk with only 7k miles on it, I bought it brand new in 2000. The front cylinder is firing very intermittently, more off than on. After idling for a few minutes the rear header gets hot to the touch but the front is barley warm. It is intermittent during idle and high revs. Gas or starting fluid directly into the carb does not make it fire. New plugs and spark looks good to me.
Local Honda shop verified spark and even replaced a coil as they say it was on the weaker side of specs. They say they had carbs off many times, for cleaning, ect but finally realized the issue. Since it was jetted the 3rd party jets are made of harder material which has worn the carb body thereby allowing too much fuel to leak past? To fix it requires a new carb but they are no longer made. They suggested most used carbs would be also jetted and would have similar issues. This diagnosis seems really far out there to me.
When riding it and the front cylinder does kick in it pulls like it always has but only maintains that state for a few seconds. Also manually adding fuel or starting fluid having no impact seems to suggest ignition to me even though spark looks good.
I have read so many forum threads at this point but still not sure where to go from here. As of now I have the tank, air box and fairing off. Suggestions much appreciated.
Local Honda shop verified spark and even replaced a coil as they say it was on the weaker side of specs. They say they had carbs off many times, for cleaning, ect but finally realized the issue. Since it was jetted the 3rd party jets are made of harder material which has worn the carb body thereby allowing too much fuel to leak past? To fix it requires a new carb but they are no longer made. They suggested most used carbs would be also jetted and would have similar issues. This diagnosis seems really far out there to me.
When riding it and the front cylinder does kick in it pulls like it always has but only maintains that state for a few seconds. Also manually adding fuel or starting fluid having no impact seems to suggest ignition to me even though spark looks good.
I have read so many forum threads at this point but still not sure where to go from here. As of now I have the tank, air box and fairing off. Suggestions much appreciated.
07-13-2017, 04:15 PM
#2
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Wow, the stealerships diagnosis doesn't seem right to me either... Those are some very weird symtoms, i agree with you on the probability that it's spark related, but if the spark tests out okay then how could it be that ?... could the timing be off badly enough for the rear cylinder to still run ok, while the front cylinder has a valve open on the compression stroke and literally squeezes all the air/fuel mix out before it can be detonated ? My input is literally just a shot in the dark, im not a mechanic professionally...
Last edited by MaineHawk; 07-13-2017 at 04:19 PM.
07-13-2017, 05:04 PM
#3
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Pick up a different carb. Look on the bay or get one from here as Beau is parting 2 Hawks at the moment (see classifieds). Maybe find a different shop too.
Very weird diagnosis. Never heard of the carb body wear issue. Did they strip jet threads in the carb?
Very weird diagnosis. Never heard of the carb body wear issue. Did they strip jet threads in the carb?
07-13-2017, 09:07 PM
#4
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I had worn emulsion tubes on my RF900, the slide rattles and the stock needle wears what should be a perfect circular hole into an ellipse. Symptoms from this were very rich running at low revs, occasional fouled plugs and a heavy appetite. New emulsion tubes fixed that right up and range per tank when from 180 to 260km.
Your symptoms don't sound anything like that; I reckon they are electrical in nature hence the on/off appearance. I'd suggest checking the low tension coil wire for the front head back to the igniter unit in the tail for continuity/terminal corrosion.
Your symptoms don't sound anything like that; I reckon they are electrical in nature hence the on/off appearance. I'd suggest checking the low tension coil wire for the front head back to the igniter unit in the tail for continuity/terminal corrosion.
05-10-2018, 11:52 AM
#5
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Fixed It!
Hi everyone,
Thanks for the suggestions. I purchased a set of carbs from eBay and was set to replace them. Upon taking the fairing off I noticed the new coil had been installed on the working rear cylinder. I swapped the coils and the problem followed the coil. I purchased a replacement part from partzilla and the issue has been remedied. It is running on both cylinders now.
Unfortunately the bike is running very lean; it is a bit weak and backfiring on deceleration. The shop had informed me when I picked it up that they adjusted for the problem the best they could which means they leaned it out I am guessing. So frustrating that a shop could be so incompetent. I went there to let them know what had happened and the entire service staff was new. I spoke with the gm and he admitted they had problems with the previous staff but stopped short of making it right. I'll be trying my hand at tuning the carbs now, not trusting shops ever again. Thanks!
Thanks for the suggestions. I purchased a set of carbs from eBay and was set to replace them. Upon taking the fairing off I noticed the new coil had been installed on the working rear cylinder. I swapped the coils and the problem followed the coil. I purchased a replacement part from partzilla and the issue has been remedied. It is running on both cylinders now.
Unfortunately the bike is running very lean; it is a bit weak and backfiring on deceleration. The shop had informed me when I picked it up that they adjusted for the problem the best they could which means they leaned it out I am guessing. So frustrating that a shop could be so incompetent. I went there to let them know what had happened and the entire service staff was new. I spoke with the gm and he admitted they had problems with the previous staff but stopped short of making it right. I'll be trying my hand at tuning the carbs now, not trusting shops ever again. Thanks!
05-10-2018, 01:11 PM
#6
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Local Help?
Where in the US are you? Perhaps we have a SH experienced owner near by that can assist.
What is the location and name of the dealer that gave you the story of hard jets wearing out the carb (what utter BS, it literally is not possible, the "jets" are fixed in place, they do not move, I might see a jet needle being worn as it does no matter what jet is installed, but jet needles are cheap and easy to get)
What is the location and name of the dealer that gave you the story of hard jets wearing out the carb (what utter BS, it literally is not possible, the "jets" are fixed in place, they do not move, I might see a jet needle being worn as it does no matter what jet is installed, but jet needles are cheap and easy to get)
05-10-2018, 01:46 PM
#7
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Thanks! The mechanic specifically blamed the needle as part of the jet kit for wearing out carb body thereby allowing too much fuel. Still total BS. This was Honda of Michigan City Indiana, the zip is 46360. I live in the area. I've not seen another SH around, would love to know of any other owners near.
05-10-2018, 02:21 PM
#8
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Yeah what a load they tried to feed you.
A couple things.
Using aftermarket jets is a non-issue.
The bit that wears in these carbs is the needle jet. It can not be replaced, though doesn't usually wear much unless you don't maintain the small foam filters in the airbox.
The emulsion tubes do not wear in these carbs.
With all that there is a carb set up thread but the cliff notes are leave them basically stock. Possibly go up one size on the pilots and maybe a shim on the needles, if needed and that is about it.
Then check the TPS setting and go ride.
A couple things.
Using aftermarket jets is a non-issue.
The bit that wears in these carbs is the needle jet. It can not be replaced, though doesn't usually wear much unless you don't maintain the small foam filters in the airbox.
The emulsion tubes do not wear in these carbs.
With all that there is a carb set up thread but the cliff notes are leave them basically stock. Possibly go up one size on the pilots and maybe a shim on the needles, if needed and that is about it.
Then check the TPS setting and go ride.
05-11-2018, 06:14 AM
#9
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Thanks! The mechanic specifically blamed the needle as part of the jet kit for wearing out carb body thereby allowing too much fuel. Still total BS. This was Honda of Michigan City Indiana, the zip is 46360. I live in the area. I've not seen another SH around, would love to know of any other owners near.
Lets see, the stock needle is STEEL and they do not typically wear out a emulsion tube (AKA a needle jet) (non replaceable on these carbs...kind of more later) but the softer brass aftermarket one did... Yaaa, ahh, no...
That said, the needle jet may have been worn out... I have a set of VTR carbs that that needle jet is oval on the front carb.
The needle jets ARE replaceable , but it is a machining operation, not user friendly.
We have one user that had his carbs modified with new needle jets and needles from Factory Pro... And I have a set of carbs that had the needle jets replaced.... but they were done in a machine shop that makes carbs from a blocks of billet aluminum for fun and does things like boring the throat of a carb on a daily basis. They removed the stock needle jets, made new ones and fitted them in place for me..... It would have been $700~$1000 job I bet had I been a paying customer..
And its not a performance thing like the Factory Pro deal.
If you have needle jets that are no longer round, buy a good used set of carbs, or consider the Factory Pro deal,,,but read the saga of having those installed and then the bike tuned before you do that
https://www.superhawkforum.com/forum...dle-jet-32573/
EDIT.. Interesting.... Factory Pro has pulled done the HDJ product pages that once advertised their service of installing HDR needle jets in carbs like ours.
They now on their site anyway only offer the HDJ needle jet for the FCRMX carb which is a screw in replaceable part.
Last edited by E.Marquez; 05-11-2018 at 06:26 AM.
05-11-2018, 03:12 PM
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Then make the tooling to put it back in, but it can be done.....though bring your wallet
I tell folks they are not replaceable because you can still buy a new set of carbs for less.
05-12-2018, 07:44 AM
#11
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Well anything can be done but also Keihin never offered a replacement part for the jet, so along with machining the old one out you need to design and manufacture your own replacement jet.
Then make the tooling to put it back in, but it can be done.....though bring your wallet
I tell folks they are not replaceable because you can still buy a new set of carbs for less.
Then make the tooling to put it back in, but it can be done.....though bring your wallet
I tell folks they are not replaceable because you can still buy a new set of carbs for less.
And now that Factory Pro may no longer be an option, I think it is completely a not possible deal (short of like you said a one off job at a machine shop... and Id say your right, that job will cost about the same as sourcing a good set of FCRs for our bike)
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