What on Earth happened?!
I've been riding the '86 700 with only the choke circuit needing another cleaning, but putting it off while I prepared the Vmax for sale (it had been taken quite a ways from stock and nobody is going to buy a pink Vmax with rearsets and clip-ons, I'm putting it back to stock the way I bought it).
So I rode the VFR to work, same little dance to get it warmed up but after that it was its sweet, easy-revving self.
After work, I cranked and cranked, tried and tried, no start. Just when I went to call for a truck, I gave it one more try and it sprang to life, pretty as you please, at least as pretty as it could with the choke circuit still clogged. Normal at least.
It rode horribly though, lunging and surging and popping on acceleration, which means it got really lean even though nothing's been touched.
What could change so quickly? It's always idle that suffers when a piece of funk breaks loose in the carbs...but it was idling just fine, instead it won't rev well now without the surging and popping, and a long delay after the throttle is closed for the rpm's to come down. It's popping so much that I'm concerned about causing top end damage and I've parked the bike till I figure this out.
If a carb boot cracked during the day, would it explain this? A sudden vacuum leak? Nobody seems to have bothered the bike...could something have gotten into the fuel that the filter can't catch? Water? It DID rain heavily the day before but the bike got me to work just fine.
No way the popping is a coil gone bad...right? I can't imagine a bike with such low miles has a bad coil, or that a bad coil would show itself in this manner....but I'm no mechanic.
I'd appreciate any voices of experience here, thanks....
[image: View Post]coffeebrake, on 08 November 2010 - 07:17 PM, said:
What on Earth happened?!
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I'd appreciate any voices of experience here, thanks....
Could be cracked or loose boot, but what about...
rust, crud or varnish in the fuel tank
crud getting into the carb bowl clogging all circuits--inlet float valve, pilot, main, enrichment (choke)
Trying to ride when you know you have a problem in the carbs is a good way to get stranded, as you found out...
Just do it, clean em properly and be done with it.
Sure enough...but I don't have a car and one bike is down (out of my three streetable machines). I can't work on more than one at a time in my tiny garage, and didn't want to let the VFR set up as that's the worst thing to do to a bike, leave it unridden with fuel in the system. Besides, I really think very highly of it, it makes me giggle. :wub:
Vmax is a clutch line away from stock and will be out of the way (and for sale!) by morning, then I can roll in the VFR and yank the carbs again. Meanwhile the Honda Nighthawk is my only bike in perfect working order right now...it never leaves me stranded, I swear it loves me.
Don't get me wrong, I'm not being lazy and don't need a scolding. I work hard to take care of my old bikes and keep them on the road and safe to ride. Just inexperienced with this particular carb issue is all, and not in a position to hire it done and wouldn't if I could.
I'm most interested in the fact that this was very sudden, just on/off with this problem. The fuel filter is clean and the tank is remarkably good inside, I don't see how crud from the tank could get to the carbs with a fuel filter in place. Not that it can't, I just don't know how.
Oh yeah, the petcock began to leak when switched to "reserve" on the same day. Is fuel starvation, like if the fuel pump can't get enough fuel because the petcock is letting air into the lines....would that possibly make it do that?
Don't worry, carbs are coming off to get that choke circuit clean, the work doesn't scare me...but I would really like to know all I can about what other folks have found and fixed so I can get it done right.
[image: View Post]JBAXX, on 09 November 2010 - 02:05 AM, said:
Sounds like the petcock diaphragm is leaking and should be checked/replaced. Could definitely cause a fueling issue.
Sadly there is no diaphragm that I can access. The petcock under the big knob thing is just a weird three-hole o-ring that I will never be able to find, and a sealed petcock that looks like any normal petcock.
I don't see any way to fix the petcock, other than buy a $50 replacement one.
It was leaking a steady drip drip drip, fuel all over me and the bike.
But there was still lots of fuel in the tank, so the engine wasn't running dry.
Popping on accelleration....could that be fuel starvation?
K&L has a lot of petcock rebuild kits/parts. I don't see them on their website, so you will have to just call them or download the 94MB parts catalog. :blink:
[image: View Post]coffeebrake, on 08 November 2010 - 10:30 PM, said:
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Oh yeah, the petcock began to leak when switched to "reserve" on the same day. Is fuel starvation, like if the fuel pump can't get enough fuel because the petcock is letting air into the lines....would that possibly make it do that?
Don't worry, carbs are coming off to get that choke circuit clean, the work doesn't scare me...but I would really like to know all I can about what other folks have found and fixed so I can get it done right.
Not trying to scold ya...sorry if it came across that way.
Okay now this would have been the most important observation to report initially. You have a blockage in the fuel line possibly from rubber oring material or other crud. That is why you are running lean--no fuel is getting from the tank to the carbs.
I have had very poor results from KandL rebuild kits. Even if I polish every metal part meticulously, anything fuel-related from KandL seems to fail prematurely. I like everything else they make, but not anything that touches fuel. Still, I really need something for this bike....
So it WOULD pop on accelleration if the pump is sucking air from the petcock?
And...I don't see a vacuum line for this tank. When it's on, fuel pours even when the lines are disconnected, so it's not operating on vacuum. There is no line from the petcock to be a vacuum line. As I understand it, this system is gravity feed to the fuel pump, which feeds the carbs.
The filter looks great, it's 25 years old and stock, I can see no funk in there. The firs thing I did was drain year-old fuel out of it when I got the bike, and no funk came out at all. Looks good inside too. PO had been emptying the tank every year up until the last year, when it gummed up the carbs.
The pump seems to be working OK, not sure how to test its output but it certainly clicks and does its thing when the bike is on, when it needs to go to reserve, and when I forget to turn the fuel on.
[image: View Post]coffeebrake, on 09 November 2010 - 11:28 AM, said:
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The filter looks great, it's 25 years old and stock, I can see no funk in there.
The thing is when dealing with old bikes, it is a lot easier to troubleshoot, repair and get em on the road if you just go ahead and replace all the rubber tubing and filters and anything else that will deteriorate or clog up over time and when exposed to gasoline, varnish and oil residue. Nothing lasts forever and 25 years is a long time in the lifetime of plastic and rubber stuff. If you are having fuel issues don't assume anything is good unless you put it in fresh, or cleaned it yourself, etc. Otherwise you will be chasing your tail...
Temporarily bypass as much as you can--go directly from tank to carbs with a piece of clear tubing so you can see the gas go into the carbs, then see if it will start, etc. Don't recommend riding like that, just for troubleshooting to find where the blockage might be...
Of course finishing the Vmax took way longer than I thought, so I didn't get to touch the VFR today but ya'll's responses have added to what I need to look at anyway, thanks.
I'll pick up a fuel filter this evening, is there any requirement for flow or anything like that?
Where do you source a fuel filter for this thing? It has really bid ID for the fuel lines and the regular fuel filters don't work.
Again, I can blow in the stock filter and get just as much flow as through the new one that is too small to fit.
More importantly:
The carbs are off and I'm trying to get through the enrichment circuit. I understand that it is found near where the jets are in the bowl, the tube that cannot be removed. I can feed a very tiny wire (from the dulcimer strings) down maybe three inches, then it stops. Is it supposed to come out somewhere?
It seems it should come out at the airbox side of the carbs, but when I feed the same wire down that hole, it also goes in about 2 inches and stops.
Finally, do I need to remove the choke plungers to properly clean the choke circuit? I'm not sure where this circuit goes or how to clean it....
End of thread · 13 posts recoveredWayback Machine snapshot 4 Jun 2011