PDA

View Full Version : VT/VTZ engines and the fuel tap



El Dopa
23rd October 2005, 13:27
Right, just got my VTZ back with a new (2nd hand) engine in it. Had a quick chat with the mechanic before I rode off, and he mentioned something interesting that might be handy for VT/VTZ owners, especially the older models.

Apparently, leaving the fuel tap in the open/run position for extended periods (e.g. overnight etc) when the engine isn't running, has the potential to screw your engine something chronic - the big end goes, basically.

If that happens, you'll almost certainly need to replace the engine, which is what I've had to do twice. The fuel tap is now the no.1 suspect for both of these blow-ups

The bikes are supposed to have a safety feature to stop this happening, but it doen't always work. So the lesson is: always turn off your fuel tap when not runing the bike.

Coyote
23rd October 2005, 13:32
Could this also apply to other bikes?

onearmedbandit
23rd October 2005, 13:33
*sniff sniff* smells like bullshit to me. Did he give you any reason why petrol in the carbs can cause your engine to blow up? On two-stroke engines you should switch the full tap off, to avoid flooding, not to avoid bowing the motor up.

Or maybe he's onto something................................

Ixion
23rd October 2005, 14:15
Well, a lot of Jap bikes don't actually have an OFF position. They're controlled by a diaphragm off manifold vacuum and only have ON RESERVE and PRIME (and jolly annoying it is too).

As to why : well I don't know , but maybe on a V Twin where the carb is often physically higher than the inlet port, if the carb flooded, and the fuel ran past an open inlet valve, it could seep down past the rings into the sump, diluting the oil and reducing its effectiveness? Maybe ?

onearmedbandit
23rd October 2005, 14:25
That's the only possible conclusion that I could draw as well Ixion, the only way the big-end could be affected. Anyone else heard of this problem, surely it would be well documented if it did exist?

FROSTY
23rd October 2005, 14:51
El Dopa ol son--The advise offered to you was (I believe) specific to YOUR bike.
your carb needles are pretty worn and your fuel tap is a tadd dodgy.
What's happening is whilst the bike is standing fuel is indeed running into the sump and your bigends are sitting in a pool of petrol rather than oil.
I'd almost suggest you fit one of those big lawnmower taps inline from your tank then turn the tap off and run your bike dry of gas.
Only applies when you leave it standing for long periods
-In case anyone wants to flame me--I know the bike I know the mechanic and I know the situation almost as well as Mr Dopo Himself.

TLDV8
23rd October 2005, 15:04
Right, just got my VTZ back with a new (2nd hand) engine in it. Had a quick chat with the mechanic before I rode off, and he mentioned something interesting that might be handy for VT/VTZ owners, especially the older models.

Apparently, leaving the fuel tap in the open/run position for extended periods (e.g. overnight etc) when the engine isn't running, has the potential to screw your engine something chronic - the big end goes, basically.

If that happens, you'll almost certainly need to replace the engine, which is what I've had to do twice. The fuel tap is now the no.1 suspect for both of these blow-ups

The bikes are supposed to have a safety feature to stop this happening, but it doen't always work. So the lesson is: always turn off your fuel tap when not runing the bike.

What can also happen if fuel gets past the needle seat is fill the cylinder if the inlet valve/valves are open which then can hydraulic and bend a conrod or worse... Depends if it is a manual or vacuum operated fuel tap,i seem to remember CBX's could do the above,so it was reccommended to turn the tap to off when not in use. ???..I remember a mate with a mexico escort who did some heater mods and wondered why the wheels were locking up when it was towed trying to restart it,a heater hose had been connected to the inlet manifold filling the cylinders.

El Dopa
23rd October 2005, 16:16
El Dopa ol son--The advise offered to you was (I believe) specific to YOUR bike. Your carb needles are pretty worn and your fuel tap is a tadd dodgy.
What's happening is whilst the bike is standing fuel is indeed running into the sump and your bigends are sitting in a pool of petrol rather than oil.

Yes, but mine is probably not the only clapped out old VT on this site. Anyone else riding one might want to have a look at their fuel tap and carbs, and possibly save themselves some expensive hassle. That's the only reason I was posting it.



-In case anyone wants to flame me--I know the bike I know the mechanic and I know the situation almost as well as Mr Dopo Himself.

And just to clarify, this wasn't a backhanded crack at the mechanic. I have NO problem with him or his work.

El Dopa
23rd October 2005, 16:24
Only applies when you leave it standing for long periods


P.S. If that isn't a bloody good reason to ride it all the time, I dunno what is. :niceone:

FROSTY
23rd October 2005, 16:30
Yes, but mine is probably not the only clapped out old VT on this site. Anyone else riding one might want to have a look at their fuel tap and carbs, and possibly save themselves some expensive hassle. That's the only reason I was posting it.
And just to clarify, this wasn't a backhanded crack at the mechanic. I have NO problem with him or his work.
Never thought it for even a nanosecond mate---honest injun.
But ya do make a good point--and I guess it doesn't just apply to VT's

limbimtimwim
23rd October 2005, 23:57
The bikes are supposed to have a safety feature to stop this happening, but it doen't always work. So the lesson is: always turn off your fuel tap when not runing the bike.Hrrm.. My fuel tap is faulty for sure, it pisses gas with no vacuum applied to the vacuum hose that should prevent it. Never thought it would do that, makes a hell of a lot of sense really.

I'm off to the garage now to turn off that tap.

And I'll do an oil and filter change tomorrow.

Mr Dopa, what were the signs of your engine failure(s), ya know, before it went boom..

nudemetalz
24th October 2005, 13:01
Hrrm.. My fuel tap is faulty for sure, it pisses gas with no vacuum applied to the vacuum hose that should prevent it. Never thought it would do that, makes a hell of a lot of sense really.

I'm off to the garage now to turn off that tap.

And I'll do an oil and filter change tomorrow.

Mr Dopa, what were the signs of your engine failure(s), ya know, before it went boom..

Haven't you done that oil change yet ??? You norty boy !!!!!

Bonez
24th October 2005, 14:07
I've left my gsx750et tap on prime overnight once and emptied the contents of the fuel tank into the sump. Wouldn't turn over at all. Needless to say I check the oil level and fuel tap before EVERY ride on it now.

greenman
24th October 2005, 14:35
This problem happens to the GPz900r, the fuel tap becomes faulty and doesn't turn off completely, the carb needles then let the float bowls overflow into the engine. Then when you try to turn it over the next day the engine makes a very loud bang, and you've got yourself a bent conrod. This usually happens to the No 1 cylinder.
Go to the GPz900 website, and take a look at the photos of this.

El Dopa
24th October 2005, 20:12
Mr Dopa, what were the signs of your engine failure(s), ya know, before it went boom..

First time, nothing until I was riding along one fine day, and the engine randomly decided to spray hot green cooling fluid all over my crotch. Fortunately I was wearing my asbestos underwear.

After that, no power and a ride home in Frostys van.

Second time. Well, with hindsight, the first warning sign was probably when the engine wouldn't turn over. I had a quick look at the carbs and the rear one was all gummed up and sticky with leaking crap all over it. Being a dickhead, and at the time undereducated in the ways of carbs, I wiped it off, and managed to jumpstart the bike. Sweet. As soon as the engine was running again, I conveniently forgot all about the carb and the muck (cos there was this ride I really, really wanted to go on). Halfway through the ride, the engine blew up again. Doh.

So, if she won't turn over, have a look at your carbs. If they're covered in crap (especially the rear one), that's your first sign.

Then, have a look at your oil level. If it's higher than it should be, it's not because the pixies have been filling it for you, it's because petrol is leaking into the sump.

The engine is probably (??) salvagable at this point, but only if you don't ride the bike. Dunno what the fix is, but it probably involves draining/stripping out the pistons and cleaning everything up.

DISCLAIMER: The above is hard won recent knowledge and is probably wrong. If it is, would someone wiser than me correct it.

EDIT: I will also be looking inot replacing the fuel tap ASAP, and possibly the carbs, if it isn't too expensive.

limbimtimwim
25th October 2005, 13:17
Haven't you done that oil change yet ??? You norty boy !!!!!I was looking after the parents's dog all weekend. And I can't make a mess out of their nice driveway. If I sneak out of work early this evening..
First time, nothing until I was riding along one fine day, and the engine randomly decided to spray hot green cooling fluid all over my crotch. [....] cent knowledge and is probably wrong. If it is, would someone wiser than me correct it.No, nothing like that going on. When I had the carbs out <month ago (Before they got cleaned) to my un-educated eyes they looked like they should for 38,000ks of use. And they oil level is in the right place. But I think I'll leave that tap off anyway.

Thanks, useful stuff in your post for future generations to use :-)

Phurrball
25th October 2005, 13:42
Dude! You just don't deserve such ill luck with that bike 'tis just not fair!


P.S. If that isn't a bloody good reason to ride it all the time, I dunno what is. :niceone:

Sounds like the plan!

I sympathise with leaky fuel issues - Mrs P's FXR decided to leak the precious contents of its tank on to the ground in the weekend. Tank drained (into jerry can), removed and hopefully off to Coleman's today - pretty minor I think.

(heads up if you're reading this Sarge - be seeing you later today after work...)

NordieBoy
25th October 2005, 13:51
Wasn't it a general problem with the VT's that one of the big ends would go at about 30,000km?

nudemetalz
25th October 2005, 14:34
Wasn't it a general problem with the VT's that one of the big ends would go at about 30,000km?

Yes they do have issues with the crank, but I think that's exacerbated (nice big word !!) by lack of frequent oil changes. That goes for most Hondas of that era anyway. My previous VT and my current VT (R) haven't had or got any funny knocking noises and I have left the petrol to "on" on both with no issues.