Poor performance - stuttering at 5,000rpm
12-13-2008, 08:59 PM
#1
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Squid
Thread Starter
Join Date: Dec 2008
Posts: 9
Poor performance - stuttering at 5,000rpm
hello lads, my name is Darren and I'm in Tipperary in Ireland. I joined this site tonight out of sheer desperation.
I have a 1998 VTR Firestorm that I bought about three months ago and has given me non-stop trouble that is literally driving me insane. I've spent money, I've spent time, I've had several people try and help me.
The bike stutters and and performs as if it has fuel starvation problems. It ticks over and pulls through the revs great, but if you cruise along at a constant rev, in around 3,500 to 5,000 rpm she stumbles and misses. If you crack open the throttle she will take off fine, but at constant speed is terrible.
Now before you start screaming things like vacuum lines on the spout facing downwards and PAIR valves etc - let me explain! this kinda talk is old news to me pal!
my bike is strange because when I bought her she had a half a PAIR system that was disabled poorly. My rear rocker cover had a mysterious hose coming from the little silver cover that houses the reed valve, a hose going nowhere and it looked as if there was nowhere it should go. So the obvious thing was to check the front rocker cover, right? well the front rocker cover has no reed valve, little silver cover or anything - nothing. the casting marks are on the rocker cover as if Honda had intended to put one there, but no PAIR, and obviously, no hole.
so, i noticed after sometime driving the bike that the PAIR at the back was venting out an oily mist. I drive the bike everyday, about an 80 mile trip to uni, and she was being made to work for a living. she was performing poorly consistently. so this is what aroused suspicion and I discovered the wonderful world of PAIR valves and subsequently closed the valve and drove off into the sunset.
she seemed to perform slightly better, i synced up the carbs and everyhting seemed well. she was noticably popping more on the throttle over run, but i like that and was happy.
however, today she is back to her old tricks and is driving worse than ever. i've gone through plugs, i've disassembled carbs and cleaned and balanced them a hundred times in the last few weeks. new airfilter. new Samco coolant hose kit. new APE cct's. new vacuum hoses etc.
but i am getting nowhere.
I notice that the owner of a page called 'Greg's Liter Honda Bikes' is on this site and I must say that I found all the info most helpful there and it was the best resource I could find anywhere on the VTR Firestorm and I tried hard, very very hard, because I need this bike. actually, while I mention it, the page seems to be offline tonight. Today I changed the routing of the little hoses under the carbs, I think its called 'VTR Carb Fix' on Greg's page. I wanted to come back and see if I definately did it right, but have had no luck getting into the page all evening.
Its 5am in Ireland and I should have been asleep long ago, but I'm back on the bloody net trying to get some info that can help. I'm getting desperate, i'm a student and i sank every penny i could milk into this bike that i waited for for ******* ages and now its a nightmare!
I have a 1998 VTR Firestorm that I bought about three months ago and has given me non-stop trouble that is literally driving me insane. I've spent money, I've spent time, I've had several people try and help me.
The bike stutters and and performs as if it has fuel starvation problems. It ticks over and pulls through the revs great, but if you cruise along at a constant rev, in around 3,500 to 5,000 rpm she stumbles and misses. If you crack open the throttle she will take off fine, but at constant speed is terrible.
Now before you start screaming things like vacuum lines on the spout facing downwards and PAIR valves etc - let me explain! this kinda talk is old news to me pal!
my bike is strange because when I bought her she had a half a PAIR system that was disabled poorly. My rear rocker cover had a mysterious hose coming from the little silver cover that houses the reed valve, a hose going nowhere and it looked as if there was nowhere it should go. So the obvious thing was to check the front rocker cover, right? well the front rocker cover has no reed valve, little silver cover or anything - nothing. the casting marks are on the rocker cover as if Honda had intended to put one there, but no PAIR, and obviously, no hole.
so, i noticed after sometime driving the bike that the PAIR at the back was venting out an oily mist. I drive the bike everyday, about an 80 mile trip to uni, and she was being made to work for a living. she was performing poorly consistently. so this is what aroused suspicion and I discovered the wonderful world of PAIR valves and subsequently closed the valve and drove off into the sunset.
she seemed to perform slightly better, i synced up the carbs and everyhting seemed well. she was noticably popping more on the throttle over run, but i like that and was happy.
however, today she is back to her old tricks and is driving worse than ever. i've gone through plugs, i've disassembled carbs and cleaned and balanced them a hundred times in the last few weeks. new airfilter. new Samco coolant hose kit. new APE cct's. new vacuum hoses etc.
but i am getting nowhere.
I notice that the owner of a page called 'Greg's Liter Honda Bikes' is on this site and I must say that I found all the info most helpful there and it was the best resource I could find anywhere on the VTR Firestorm and I tried hard, very very hard, because I need this bike. actually, while I mention it, the page seems to be offline tonight. Today I changed the routing of the little hoses under the carbs, I think its called 'VTR Carb Fix' on Greg's page. I wanted to come back and see if I definately did it right, but have had no luck getting into the page all evening.
Its 5am in Ireland and I should have been asleep long ago, but I'm back on the bloody net trying to get some info that can help. I'm getting desperate, i'm a student and i sank every penny i could milk into this bike that i waited for for ******* ages and now its a nightmare!
12-13-2008, 09:13 PM
#2
Moderator
MotoGP
Join Date: May 2005
Posts: 2,708
The pair valve allows frsh air into the exhaust... nothing more. I've seen them blocked off every which way and it's never made a difference in performace. To me, it sounds like it's running very rich. Does the bike have any modifications? If you're cruising along and it's stuttering, then you intruduce a bunch of air via the throttle and it clears it up... signs point to a rich condition. Try pulling the choke out and see if it gets better or worse.
12-13-2008, 09:40 PM
#6
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MotoGP
Join Date: Aug 2007
Location: Way Out West
Posts: 2,547
Is the air filter the standard Honda? Air box is stock? Which exhaust system are you running?
Are the carb internals stock or rejetted? And which main jets and needle position if rejetted?
Have you checked the TPS with a multimeter?
Are the carb internals stock or rejetted? And which main jets and needle position if rejetted?
Have you checked the TPS with a multimeter?
12-13-2008, 10:02 PM
#8
Junior Member
Squid
Thread Starter
Join Date: Dec 2008
Posts: 9
i reset the TPS with the multimeter.
the first day I had the bike I fried the R/R and it took out the battery and the TPS with it. I replaced it with the Yamaha R1 unit and got a secondhand TPS which was functioning perfectly and that is all fine now. the electrics are all good, i'm positive of that. a friend who has another VTR let me swop out the ECU, the coils etc and it all made no difference.
the strange thing is it is erratic sometimes. sometimes the bike will drive well for hours and suddenly start performing terribly and it can last for days.
the first day I had the bike I fried the R/R and it took out the battery and the TPS with it. I replaced it with the Yamaha R1 unit and got a secondhand TPS which was functioning perfectly and that is all fine now. the electrics are all good, i'm positive of that. a friend who has another VTR let me swop out the ECU, the coils etc and it all made no difference.
the strange thing is it is erratic sometimes. sometimes the bike will drive well for hours and suddenly start performing terribly and it can last for days.
12-13-2008, 10:19 PM
#9
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MotoGP
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Location: Way Out West
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I was going to guess that the guy who botched the pair removal had buggered a carb rejet as well, but if the air filter is Honda and you know the jetting is stock, it must be something else.
If the vacuum line to petcock is fine, petcock isn't gummed up etc. and especially because it is intermittent it sounds more electrical than fuel, but I don't know what it would be.
If the vacuum line to petcock is fine, petcock isn't gummed up etc. and especially because it is intermittent it sounds more electrical than fuel, but I don't know what it would be.
12-14-2008, 02:19 AM
#10
Senior Member
SuperSport
Join Date: May 2008
Location: Central Fl.
Posts: 530
Does the hesitation continue above 5K rpm?
I have a dent in my forehead from slapping myself while diagnosing my own motorcycle ailments these last forty years. (I am a slow learner)
Is the fuel tank vent clear?
Is the vacuum line to the petcock intact along it's entire length and doesn't collapse under hard vacuum?
Ireland? Moist ambient sea air? Have you made sure that there is no corrosion on any of the connectors to the CPU box or the ignition system? I found corrosion in the connection junction between the female pin and the red/white wire for the RR unit that prevented my bike from charging the battery despite installing a new RR.
Diaphrams in the carbs okay? My BMW had a slight tear in one that caused the same symptom that you describe.
As my dent grows deeper, I wish you luck over there. Having a touch of Irish in me, I've always had a slight yen to visit. Perhaps someday.
I have a dent in my forehead from slapping myself while diagnosing my own motorcycle ailments these last forty years. (I am a slow learner)
Is the fuel tank vent clear?
Is the vacuum line to the petcock intact along it's entire length and doesn't collapse under hard vacuum?
Ireland? Moist ambient sea air? Have you made sure that there is no corrosion on any of the connectors to the CPU box or the ignition system? I found corrosion in the connection junction between the female pin and the red/white wire for the RR unit that prevented my bike from charging the battery despite installing a new RR.
Diaphrams in the carbs okay? My BMW had a slight tear in one that caused the same symptom that you describe.
As my dent grows deeper, I wish you luck over there. Having a touch of Irish in me, I've always had a slight yen to visit. Perhaps someday.
12-14-2008, 05:17 AM
#12
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SuperBike
Join Date: Mar 2007
Location: Williamsburg, VA
Posts: 2,455
+1 on carb boots and diaphrams. Pull the tank off again and make sure nothing is cracked or torn. Also make sure the slides are operating as advertised, maybe they are sticking a little.
12-14-2008, 09:24 AM
#13
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SuperBike
Join Date: Feb 2007
Location: Portland, Oregon
Posts: 1,051
since the problems comes & goes i'd check the electrical connections & plugs. in moist environments i'd use dielectric grease on ALL electrical connections ( make sure you use enough to fill the connector - if you use to little you can trap moisture in and make problems worse ).
change the plugs - measure the plug wires & chech the connections. make sure you have good connections on the battery and a good ground to the chassis.
a couple of good suggestions - pulling the choke out & also checking the tank vent. also look in the tank & make sure it's clean - no rust.
tim
btw: gregs site was a HUGE help for me too when i first got my 'hawk
change the plugs - measure the plug wires & chech the connections. make sure you have good connections on the battery and a good ground to the chassis.
a couple of good suggestions - pulling the choke out & also checking the tank vent. also look in the tank & make sure it's clean - no rust.
tim
btw: gregs site was a HUGE help for me too when i first got my 'hawk
12-14-2008, 09:37 AM
#14
Out of my mind, back in 5
MotoGP
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Location: Skurup, Sweden
Posts: 6,109
Intermittent problem = 90% electrical... I'd check the grounding and connection on the ignition coils... Also the kill switch on the sidestand... That gave someone here a headache for a while...
12-14-2008, 09:40 AM
#15
2nd mouse gets the cheese
SuperBike
Join Date: Jan 2008
Location: Beaverton, OR
Posts: 1,697
sounds exactly like what mine did at 43k miles, and it ended up my coils were bad so should check those as well, the haynes manual I have details the check and its pretty easy to do just make sure you check primary and secondary circiuts on both ignition coils. I only checked primary and moved on because they tested fine only to get frustrated come back to coils and found the secondary circiut out of spec, I lost another week or so that way.
12-15-2008, 03:15 AM
#16
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Squid
Thread Starter
Join Date: Dec 2008
Posts: 9
hi guys, thanks for all your suggestions, its great to have some help.
but unfortunately i can rule out almost everyhting thats been suggested. the coils are definately good, as i swopped them out of another VTR thats going fine.
the sidestand sensor is already disabled and the vacuum lines and fuel lines are all good. i even swopped out the vacuum line with another one off a CBR600, just to be sure. the tank petcock is fine too as i checked the diaphragm and also cleaned out the pencil-filter that goes into the tank, which was spotless anyway.
i'm beginning to wonder, as a last resort, could it be the pickup coil? could it have been damaged when the R/R fried? does anyone know of a test that can be carried out to check if the pickup coil is ok without having to remove it from the bike, as its in a bitch of a place to get out.
but unfortunately i can rule out almost everyhting thats been suggested. the coils are definately good, as i swopped them out of another VTR thats going fine.
the sidestand sensor is already disabled and the vacuum lines and fuel lines are all good. i even swopped out the vacuum line with another one off a CBR600, just to be sure. the tank petcock is fine too as i checked the diaphragm and also cleaned out the pencil-filter that goes into the tank, which was spotless anyway.
i'm beginning to wonder, as a last resort, could it be the pickup coil? could it have been damaged when the R/R fried? does anyone know of a test that can be carried out to check if the pickup coil is ok without having to remove it from the bike, as its in a bitch of a place to get out.
12-15-2008, 08:45 AM
#17
Honducati
SuperSport
Join Date: Oct 2006
Location: Anaheim, CA
Posts: 809
Stock jetting and filter with slip-on exhaust can cause a lean condition in the 3-4k range. This will cause a hesitation and stutter on steady cruise. Will be worse when cold and improve as the bike warms up. If your friend has a stock exhaust, maybe you could test it by swapping it out. The solution in this case would be to rejet, or shim (raise) the carb needles to allow more fuel to flow with your aftermarket exhaust.
Also, check the carb slide diaphragms: remove the airbox cover and filter, open the slides with your finger and make sure they slide back smoothly- there should be a slight drag due to vaccum. If one of them snaps shut, there is a leak due to a damaged or mis-installed diaphragm.
Good luck and keep us updated on your progress.
Last edited by jbaxx; 12-17-2008 at 07:55 AM.
12-15-2008, 12:39 PM
#18
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Squid
Thread Starter
Join Date: Dec 2008
Posts: 9
hi jbaxx, thanks.
the carb boots are definately fine, i suspected this before and gave both a thorough inspection and was also very careful to make sure they sat right down onto the ports and that the carbs sat perfectly into them and are well tightened up so a leak is def out of the question.
i'm just home from class now and will bring in the bike and check to see what the slides are like.
she drove worse then ever today. since i reset the air/mixture jets to 2.5turns out from clockwise and rebuilt the carbs she is performing even worse. i think this rules out the pickup coil giving trouble because she is performing even worse after tinkering with the carbs.
the carb boots are definately fine, i suspected this before and gave both a thorough inspection and was also very careful to make sure they sat right down onto the ports and that the carbs sat perfectly into them and are well tightened up so a leak is def out of the question.
i'm just home from class now and will bring in the bike and check to see what the slides are like.
she drove worse then ever today. since i reset the air/mixture jets to 2.5turns out from clockwise and rebuilt the carbs she is performing even worse. i think this rules out the pickup coil giving trouble because she is performing even worse after tinkering with the carbs.
12-15-2008, 03:40 PM
#19
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Squid
Thread Starter
Join Date: Dec 2008
Posts: 9
the slides in the carbs - the back one seems to have more resistance when pushing it back. the slide on the front seems to require a little more pressure at one point in its travel, like it drags a little and then slides back easily.
it is very subtle but it is definately there.
should i pop off the cap on the front carb and have a look? i'm wary of doing it because its so difficult to get the spring back in and the disphragm/gasket to sit properly. i've never popped off the front one before, only the back.
what am i looking for apart from tiny holes if i do?
it is very subtle but it is definately there.
should i pop off the cap on the front carb and have a look? i'm wary of doing it because its so difficult to get the spring back in and the disphragm/gasket to sit properly. i've never popped off the front one before, only the back.
what am i looking for apart from tiny holes if i do?
12-19-2008, 07:54 AM
#20
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SuperSport
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Location: Hamilton, Ontario, Canada
Posts: 807
I don't think you can get the cap off the front carb without lifting both carbs out of the rubber manifolds.
One way to get the caps back on the carbs without launching one across the garage is: make sure that the screws for the cap of the carb are within easy reach. make sure you've got a phillips screwdriver or allen keywithin easy reach. put the slide in the carb and make sure the diaphragm is seated properly. invert the carb cap. get a pencil. put the eraser end of the pencil in the tube part of the carb cap. use the pencil as a guide to help get the spring into the tube in the carb cap. hold the spring in with your thumb and remove the pencil. pick up the carb cap while keeping the spring in the tube with your thumb. make sure the diaphragm is seated properly. put your other thumb under the slide and hold it so the slide doesn't move and the diaphragm doesn't shift when the spring goes in. get the tube in the cap as close as possible to the cavity in the slide before you let go of the spring. let go of the spring while holding the cap and keeping the slide stationary. seat the cap on top of the carb. you can let go of the slide but keep the cap pressed against the top of the carb so the diaphragm stays in place. install the screws. lift the slide and let it drop. it should descend steadily as the spring overcomes slight resistance. celebrate or try again. This is the procedure set out more or less in the Haynes VTR1000F manual.
One way to get the caps back on the carbs without launching one across the garage is: make sure that the screws for the cap of the carb are within easy reach. make sure you've got a phillips screwdriver or allen keywithin easy reach. put the slide in the carb and make sure the diaphragm is seated properly. invert the carb cap. get a pencil. put the eraser end of the pencil in the tube part of the carb cap. use the pencil as a guide to help get the spring into the tube in the carb cap. hold the spring in with your thumb and remove the pencil. pick up the carb cap while keeping the spring in the tube with your thumb. make sure the diaphragm is seated properly. put your other thumb under the slide and hold it so the slide doesn't move and the diaphragm doesn't shift when the spring goes in. get the tube in the cap as close as possible to the cavity in the slide before you let go of the spring. let go of the spring while holding the cap and keeping the slide stationary. seat the cap on top of the carb. you can let go of the slide but keep the cap pressed against the top of the carb so the diaphragm stays in place. install the screws. lift the slide and let it drop. it should descend steadily as the spring overcomes slight resistance. celebrate or try again. This is the procedure set out more or less in the Haynes VTR1000F manual.
03-15-2009, 05:07 PM
#22
WERA #44
Superstock
Join Date: Jul 2007
Location: About 57 miles south of VIR
Posts: 265
Some things I've noticed while building two Hawks from salvage;
The hawk carbs are huge and can be the source of much mischief.
TPS, I've reset 3 and they come at about 850 from the factory, also have read here that to be so for others. Why? The book says they should be about 500.
Water lines are more about atomization than carb icing.
Get a jet kit. also buy some 48 primaries (not in kit) if you really want it to behave with pipes and good filter. Don't big pecker yourself into too fat on the mains. Think it out and read cause they ain't the easiest carbs to R&R.
If you don't get the jet kit, at least shim (tiny washer under needle head) the needles.
The slides have many friction surfaces that can create drag and stick. Clean them carefully to get residue and grunge off with hand hot soapy water and rinse them thoroughly and dry them. rub all sliding surfaces with a little teflon oil then wipe it dry with paper towels. The center post is also a slide for the cap tube, make sure it is squarely set and moves free.
NEVER get carb cleaner on the rubber parts or the diaphram. Wash rubber and oil lightly, then wipe dry.
Load the slide spring on a 5-6mm t-handle or similar tool, put in slide tube, lay a small screwdriver or flat tool over the end of the spring, remove the t-handle and carefully slide the cap over and into the spring, pulling the tool out at the last possible moment. Double check the diaphram o-ring seal is seated properly before screwing it together.
The foam elements in the airbox for the carb vents turn to stcky chunks and end up in the caps on top of the diaphrams.
Water is a poor substitute for gasoline, and, as gas floats on water, getting rid of it is dificult in some places. Water contamination can cause many different symptoms.
I've seen 1 hawk get a front bowl full of water from extended outside exposure, and another get some in the front bowl from hand washing with a hose.
The bowl drains are your friend.
The hawk carbs are huge and can be the source of much mischief.
TPS, I've reset 3 and they come at about 850 from the factory, also have read here that to be so for others. Why? The book says they should be about 500.
Water lines are more about atomization than carb icing.
Get a jet kit. also buy some 48 primaries (not in kit) if you really want it to behave with pipes and good filter. Don't big pecker yourself into too fat on the mains. Think it out and read cause they ain't the easiest carbs to R&R.
If you don't get the jet kit, at least shim (tiny washer under needle head) the needles.
The slides have many friction surfaces that can create drag and stick. Clean them carefully to get residue and grunge off with hand hot soapy water and rinse them thoroughly and dry them. rub all sliding surfaces with a little teflon oil then wipe it dry with paper towels. The center post is also a slide for the cap tube, make sure it is squarely set and moves free.
NEVER get carb cleaner on the rubber parts or the diaphram. Wash rubber and oil lightly, then wipe dry.
Load the slide spring on a 5-6mm t-handle or similar tool, put in slide tube, lay a small screwdriver or flat tool over the end of the spring, remove the t-handle and carefully slide the cap over and into the spring, pulling the tool out at the last possible moment. Double check the diaphram o-ring seal is seated properly before screwing it together.
The foam elements in the airbox for the carb vents turn to stcky chunks and end up in the caps on top of the diaphrams.
Water is a poor substitute for gasoline, and, as gas floats on water, getting rid of it is dificult in some places. Water contamination can cause many different symptoms.
I've seen 1 hawk get a front bowl full of water from extended outside exposure, and another get some in the front bowl from hand washing with a hose.
The bowl drains are your friend.
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