Hello, being a newby I hope I am posting this correctly, if not then apologies.
Any help, ideas or thoughts would be appreciated.
On the return from a 20 mile blast, cruising up a slight gradient doing about 40 mph the VTR just lost all power, coughed spluttered and died.
Looked in the fuel tank, the level quite low so thought I had run out. Put a gallon in the tank managed to get it going but sounded terrible, just managed to get me a mile home, no power terrible misfire.
So, stripped the carbs off had a look all pretty clean, jets clear, diaphragms ok, floats working ok.
Both plugs sparking ok.
Took rocker covers off to check valve timing ( fearing the worst as it still has Honda original cct’s ) both chains tensioned ok and all timing marks lined up ( straight edge on head was showing FI was slightly out, possibly half a tooth ).
Valve clearances checked all good on all valves on both cylinders.
Checked compression, both cylinders exactly the same at 110 psi on the starter motor( this I know is a bit low but I had to do a temporary extension to get the compression tester bulb down the plug recess so might have lost some psi on this) but the fact that both cylinders were exactly the same suggests that either they are both ok or both failed - which would be uncanny.
Put the bike back together after basically finding nothing wrong so no surprise to say that it ran terrible, exactly the same, misfiring and no power.
Changed the plugs, changed the coils, rigged up a temporary fuel tank to eliminate petcock and vapour lock issues. Exactly the same - terrible.
I have run out of ideas, what am I missing ? Any help would be appreciated.
It has been a brilliant bike that brings a smile as soon as you pull off. What a hoot.
Great forum
Dave.
Serious Misfire No Power
Re: Serious Misfire No Power
Seeing as you have checked most of the things I would have checked 
All I can think of so far is the side stand switch which can cause a misfire
In this link there is a wiring diagram so you can bypass the switch just to see if it is that, 'Tempest' explains further down how-to:
viewtopic.php?t=7275
Chris.
All I can think of so far is the side stand switch which can cause a misfire
In this link there is a wiring diagram so you can bypass the switch just to see if it is that, 'Tempest' explains further down how-to:
viewtopic.php?t=7275
Chris.
Re: Serious Misfire No Power
So now you need to find out whether the problem relates to one cylinder or both.
Without entirely removing your fingerprints, check whether both downpipes are the same temp. If one's hot and the other is colder, then whatever it is, it's on one cylinder only and you can find out whether it's fuel or sparks.
If it's both, I'd suggest you check the reg rec voltage when running.
Without entirely removing your fingerprints, check whether both downpipes are the same temp. If one's hot and the other is colder, then whatever it is, it's on one cylinder only and you can find out whether it's fuel or sparks.
If it's both, I'd suggest you check the reg rec voltage when running.
It's not falling off, it's an upgrade opportunity.
Re: Serious Misfire No Power
Thanks for the pointers, at least have a direction to go in. I will get it back together over the weekend and have a play.
I will update when I have tested the side stand and rec.
Cheers
Dave.
I will update when I have tested the side stand and rec.
Cheers
Dave.
Re: Serious Misfire No Power
Hi to all,
Just an update ( and a plea for help )
After putting the VTR back together over the weekend, alas, still running terrible.
Shorted out the side stand switch in the green connector block behind the tank, still the same, no joy.
Checked the regulator - battery voltage with the engine off 12.6 volts and with the engine running 13.9 volts so all seems ok, checked the alternator windings resistance all 0.5 ohms so all good
Checked pulse regulator resistance at connector on LH frame all good at 620 ohms.
Checked continuity from coil connectors and pulse gen. connector back to ECU all ok.
Swapped ECU and Ignition unit ( slight unknowns as they were s/h off eBay but presumed good ) no joy still the same.
Measured exhaust temp after about 5 mins of running with IR gun. Front down pipe 150 C / Rear down pipe 390 C
So, looking like a front cylinder issue. ???
Checked compression, both cylinders at 125 psi on the starter motor.
Any ideas would be good, thanks to all
Dave “frustrated”
Just an update ( and a plea for help )
After putting the VTR back together over the weekend, alas, still running terrible.
Shorted out the side stand switch in the green connector block behind the tank, still the same, no joy.
Checked the regulator - battery voltage with the engine off 12.6 volts and with the engine running 13.9 volts so all seems ok, checked the alternator windings resistance all 0.5 ohms so all good
Checked pulse regulator resistance at connector on LH frame all good at 620 ohms.
Checked continuity from coil connectors and pulse gen. connector back to ECU all ok.
Swapped ECU and Ignition unit ( slight unknowns as they were s/h off eBay but presumed good ) no joy still the same.
Measured exhaust temp after about 5 mins of running with IR gun. Front down pipe 150 C / Rear down pipe 390 C
So, looking like a front cylinder issue. ???
Checked compression, both cylinders at 125 psi on the starter motor.
Any ideas would be good, thanks to all
Dave “frustrated”
Re: Serious Misfire No Power
Checking the temperature on the pipes does mainly tell you that the carbs may need a fresh synchronization.
Next to electrical stuff I am missing any fuel related diagnostics.
Topmost troublemaker on VTRs is the membrane in the fuel petcock.
It's worth a check: disconnect the larger fuel lines - there should be no fuel coming out.
Disconnect the small hose at the back. Attach another hose, put it in your mouth and suck.
Fuel should start flowing. No flow means you need a petcock rebuild kit :-)
And there shouldn't be a significant air flow - if you can constantly get air out of that helper hose, the membrane is gone which also means a rebuild.
Next to electrical stuff I am missing any fuel related diagnostics.
Topmost troublemaker on VTRs is the membrane in the fuel petcock.
It's worth a check: disconnect the larger fuel lines - there should be no fuel coming out.
Disconnect the small hose at the back. Attach another hose, put it in your mouth and suck.
Fuel should start flowing. No flow means you need a petcock rebuild kit :-)
And there shouldn't be a significant air flow - if you can constantly get air out of that helper hose, the membrane is gone which also means a rebuild.
Bye
Martin
Martin
Re: Serious Misfire No Power
Martin,
Thanks for the input, I have sought to eliminate the fuel tap issues and the vapour lock by setting up a temporary fuel tank also a little bit of gravity to make sure the float bowls are getting fed.
Dave
Thanks for the input, I have sought to eliminate the fuel tap issues and the vapour lock by setting up a temporary fuel tank also a little bit of gravity to make sure the float bowls are getting fed.
Dave
Re: Serious Misfire No Power
You have been busy
As Tony would say, swap the HT coils around (and sparkplugs) and see if the front cylinder is then the hot one
Even brand new sparkplugs have occasionally been known to be faulty.
Seeing as you had the carbs off, are you positive they have been re-seated as in fully home on the inlet stubs?
Chris.
As Tony would say, swap the HT coils around (and sparkplugs) and see if the front cylinder is then the hot one
Even brand new sparkplugs have occasionally been known to be faulty.
Seeing as you had the carbs off, are you positive they have been re-seated as in fully home on the inlet stubs?
Chris.
Re: Serious Misfire No Power
Hi to all,
Both cylinders have a good spark at the plug, saying that, just to make sure something was not breaking down under load I have recently tried 2 new iridium plugs, swapped the coils front to back, swapped with s/h coils measured resistance of coils caps and HT leads - all to no avail ?
The carbs were fully seated when I tried it yesterday ( it would not explain the original failure when cruising along about 40mph after a perfect 20 mile run ) and no splits in the inlet rubbers.
I am thinking if the spark is good and compression is good, the rear cylinder is firing ok the ignition timing must be ok. Then it must be fuel. ??
I have just got my hands on a s/h set of carburettors, they don’t look too bad so I will give them a check over and try ( although I think I am clutching at straws ).
Dave
Both cylinders have a good spark at the plug, saying that, just to make sure something was not breaking down under load I have recently tried 2 new iridium plugs, swapped the coils front to back, swapped with s/h coils measured resistance of coils caps and HT leads - all to no avail ?
The carbs were fully seated when I tried it yesterday ( it would not explain the original failure when cruising along about 40mph after a perfect 20 mile run ) and no splits in the inlet rubbers.
I am thinking if the spark is good and compression is good, the rear cylinder is firing ok the ignition timing must be ok. Then it must be fuel. ??
I have just got my hands on a s/h set of carburettors, they don’t look too bad so I will give them a check over and try ( although I think I am clutching at straws ).
Dave
Re: Serious Misfire No Power
Swapping the coils around will tell you if it is electrical or a fuel problem.
When you checked the floats did you check that the needle valves were shutting off the fuel completely
Chris.
When you checked the floats did you check that the needle valves were shutting off the fuel completely
Chris.
Re: Serious Misfire No Power
Chris,
Yes, when I had the float bowls off, operating the floats with my finger and blowing down the fuel supply lines all worked well shutting off when the floats raised.
Dave.
Yes, when I had the float bowls off, operating the floats with my finger and blowing down the fuel supply lines all worked well shutting off when the floats raised.
Dave.
Re: Serious Misfire No Power
Check the vacuum line going to the heads. There's only one as standard, going to the rear head, but it's a common mod to fit a vac line to the front head as well, as it makes it easy to balance the carbs. If so the vac line to the front head needs to be capped off.
If either vac line is leaking it'll cause rough running.
If either vac line is leaking it'll cause rough running.
It's not falling off, it's an upgrade opportunity.
Re: Serious Misfire No Power
Yes, vacuum front vacuum line is capped off, the rear I have temporary capped off while the temporary fuel tank is in use.
Dave.
Dave.
Re: Serious Misfire No Power
We'll have you replacing the wiring loom next 
Have you checked all the earth connections are good?
There is also a cut-out switch on the clutch lever IIRC,
Chris.
Have you checked all the earth connections are good?
There is also a cut-out switch on the clutch lever IIRC,
Chris.
Re: Serious Misfire No Power
Update:
Fitted a S/H set of carbs, complete unknowns, bought them off eBay. Didn’t check them over or anything just fitted them to the bike.
The bike fired up, warmed up and ran. Woo Hoo Happy Days
Some popping and farting and sometimes erratic tick over but at least it would tick over !! Finally a step in the right direction !!
Both exhaust downpipes the same temperature at about 400 C
Any suggestions on how to set up the carbs, at least a basic set up to get it running a bit smoother before I put the bike back together ?
Also, any ideas on what could have gone wrong with my original carbs to cause such a dramatic failure. I have had them apart. They are clean with no obvious blockages, jets clean, diaphragms ok ?
Dave
Fitted a S/H set of carbs, complete unknowns, bought them off eBay. Didn’t check them over or anything just fitted them to the bike.
The bike fired up, warmed up and ran. Woo Hoo Happy Days
Some popping and farting and sometimes erratic tick over but at least it would tick over !! Finally a step in the right direction !!
Both exhaust downpipes the same temperature at about 400 C
Any suggestions on how to set up the carbs, at least a basic set up to get it running a bit smoother before I put the bike back together ?
Also, any ideas on what could have gone wrong with my original carbs to cause such a dramatic failure. I have had them apart. They are clean with no obvious blockages, jets clean, diaphragms ok ?
Dave