Fuel in vacuum pipe

BigD · Post by **BigD** » Sun May 29, 2005 11:44 pm

I have a t-piece in the vacuum pipe for carb balancing. I've been messing with the carb balancing this week and twice I have noticed petrol in the t-piece. Anyone know why this is?

Johnny Wishbone · Post by **Johnny Wishbone** » Mon May 30, 2005 9:20 am

Looks like the diaphragm in your fuel tap is perished BigD....

BigD · Post by **BigD** » Mon May 30, 2005 4:06 pm

I had a feeling it might be that, but I'm sure Del had said in a previous thread that if the diaphram had gone, fuel would be everywhere. What do you think?

Johnny Wishbone · Post by **Johnny Wishbone** » Tue May 31, 2005 9:51 am

Possibly, but I suppose it depends on how badly the diaphragm is perished. If it was very bad then I guess you would have a lot of fuel in the vac hose, but if it was just starting to go then maybe you'd just get a bit - only one way to find out!

Have you noticed a change in the perfomance of the bike at all? If there was fuel seeping into the manifold from the tap then I guess the rear cylinder might be running a little rich, but having said that it's probably not enough to make the bike feel any different.

Actually, on a similar note, for all you popping (on overrun) Stormers out there... On the way back from the NW last weekend the bike was dying over a tonne (about 5K revs) â€“ was at this the whole way from Belfast to Dublin and I couldnâ€™t figure out what was up. Anyway, just managed to get home, but on Sunday she was mis-firing badly and eventually wouldnâ€™t start at all. First impression was the rectifier was gone but when I took the tank off I noticed the fuel lines were completely dry so it was obviously fuel starvation â€“ on closer inspection I discovered that the vacuum tube from the rear intake manifold was completely perished (I only replaced it about 3 months ago!) and had a huge gaping hole in it â€“ how I got back from Portrush to Dublin with that Iâ€™ll never know!!! Replaced the tubing and instead of driving the tap diaphragm from the rear cylinder (where the tube has to do a 180 and is probably why in cracked as it cracked right on the bend) I switched it to the front cylinder where itâ€™s a straight path back to the tap and sheâ€™s fine again, but Iâ€™ve noticed that the popping on overrun is almost completely gone.

I donâ€™t know why the tubing deteriorated so quickly (itâ€™s the proper stuff, not cheapo cr@p) maybe the excessive heat is breaking it down, especially heat cycles of heating and cooling - couple that with the effects of petrol vapor which is a tube killer. The tube was also split down where it was connected to the vacuum nipple at the manifold. Iâ€™m going to replace the tubing next chance I get with beefier stuff.

Anyway, chances are, if your Storm is popping excessively and you don't have a leaky exhaust or coolant leaking at the head, then there's probably a leak somewhere on your vac hose.

BigD · Post by **BigD** » Tue May 31, 2005 7:43 pm

Johnny.

I think it is this. The bike isn't running particularly well. I have it booked on a dyno run on Friday. Popping on the new road legal cans I got recently and having problems balancing the carbs. How easy is it to change the fuel petcock

Johnny Wishbone · Post by **Johnny Wishbone** » Thu Jun 02, 2005 10:33 am

Very easy altogether - to be honest, there's no point in booking the bike in for a dyno if there's a mechanical problem since dynos are best used for setting up fueling and other 'adjustable' stuff. You're just going to end up squandering money for a pretty poor dyno print out and for some greasey spanner monkey to point out that you've leaks everywhere

If you're having trouble balancing the carbs too then it definitely looks like there's air or fuel getting in somewhere where it shouldn't.
You can take the fuel tap off the bike on a 3/4 full tank, just prop it up against something (use a towel to protect the tank by the way!) on it's front - DON'T turn it upside down as the fuel will probably seep out of the filler cap! (Speaking from experience - trust me, a burnt hole in the freshly laid lawn and a screaming girlfriend are things none of us need!

)

I think it's a 5mm Allen to get the tap off - pull it out gently as the filter is attached. Four philips screws hold on the backplate on the diaphragm chamber - pop it off carefully as the diaphragm spring will fly out. The big black rubber yoke that looks like a rolled up S&M johnny is yer man (easy Tony!)

You should also replace your vac hose too, or at least remove it and inspect it - bend and stretch it - any damage or degradation should be visible. Also, have a look at your vacuum nipple on the rear mainfold - I think it's an 8 or 10mm spanner to get it off, a socket (long reach definitely will) might fit over it actually. Remove it and replace it either with some thread lock or if you can get it, some Dirko (great stuff that!).
Also, while your at it - check the front cylinder vacuum port - it should be blanked off with a screw - again, remove and replace with some thread lock, just to be sure she's not leaking in air there too. Might also be worth checking the collars between the carbs and intake manifolds - you'll need a long reach philips screw driver, but just check that the screws on the collar are nice and tight - don't overtighten though, just hand tight.

Once you're sure your not leaking any air at your intake any further popping will point to leaks in the exhaust somewhere, most likely at the connections to the link pipes so check both ends. Disassemble, clean them and reassemble with some Dirko (it's high temp & flexible). Still popping badly? - check the headers.

Once it's all 'air tight' only then should you think about balancing the carbs and setting up the fuelling.

BigD · Post by **BigD** » Thu Jun 02, 2005 11:50 pm

Thanks Johnny. I was thinking of cancelling the dyno for the reasons you mentioned. I'd rather replace the petcock and see how it is after that.

Also, while your at it - check the front cylinder vacuum port - it should be blanked off with a screw - again, remove and replace with some thread lock, just to be sure she's not leaking in air there too.

Front cylinder has the scottoiler on it. Can this cause any problems in itself? Also Is thread lock like plumbers tape? I'm wondering if the t-piece isn't connected tightly enough/blanked off properly.

The other thing is, I don't clamp the vac pipe when balancing.

Johnny Wishbone · Post by **Johnny Wishbone** » Fri Jun 03, 2005 9:57 am

Morning BigD - good stuff, best to save your money for the Dyno until you have the bike running as best you can.

Just a thought, to tide you by for a while, you could always remove the diaphragm from the tap and plug the diaphram vacuum nipple. Also, plug the vacuum hose from the cylinder or plug the vacuum port itself. Definitely not something I'd do for very long though but at least it would mean you'd be able to get around until you got a new diaphragm... The diaphragm on my tap was stuck open for a while some months ago, and it didn't make any difference to the running of the bike. Only noticed when I removed the tank one day after turning the tap off and there was fuel p*ssing out of it

Scottoiler shouldn't cause any problems, I certainly haven't heard of any. Just check the connection at the vacuum port anyway and perhaps use some thread lock to be sure. Thread lock is a liquid glue type stuff. It doesnn't set like concrete or anything but it will stop screws from loosening as it creates a hard coat between the threads. Can be easily cleaned off after it's set too so it's by no means permanent which is good.
Dirko is a a high temperature flexible sealant, excellent for sealing exhausts, headers, etc. It's basically gasket sealer, maybe a bit stronger though.

As for the T-piece, well that falls under my previous recommendations - check everything on the vacuum line(s), tubing, connections, fittings, and T-piece(s) if installed.

I don't clamp or block off my vacuum hose either when balancing, however I have thought about the effect this might have on my readings, as one vacuum tube will have more volume that the other - theoretically if the same amount of pressure is drawn off both of them then the one with the largest volume will show the least vacuum thus giving you a false reading. Leave it with me for the weekend, I'll check the carbs with equal and unequal lengths of hose, and with the T-piece on and off and I'll tell you how I get on. Thinking about it though it shouldn't make a difference as there won't be enough time between piston revolutions to re-pressurise the tubing, certainly not over 3000rpm anyway. It should be fine, but I'll check it out.

Dave.

Pete.L · Post by **Pete.L** » Fri Jun 03, 2005 11:52 am

Johnny Said

I don't clamp or block off my vacuum hose either when balancing, however I have thought about the effect this might have on my readings, as one vacuum tube will have more volume that the other - theoretically if the same amount of pressure is drawn off both of them then the one with the largest volume will show the least vacuum thus giving you a false reading

Johny

I think you will find the volume has nothing to do with the vacuum obtained. The gauges will show the same vac it's just the time it takes to get there will be different and with the volumes involved with carb balance the time's will be negligable

Hope this helps

Pete.l

Johnny Wishbone · Post by **Johnny Wishbone** » Fri Jun 03, 2005 2:10 pm

Alright Pete me oul flower, that's what I was kind of thinking alright, since the vacuum is being pulled on the hoses repeatedly the pressure will just drop off in both and will equalise. Feck it, gonna have to find something else to do over the weekend then, other than mucking about with me bike, ah sure feckit, I'll just take her for a spin.

BigD · Post by **BigD** » Fri Jun 03, 2005 7:42 pm

Hey what about this then. Phoned the dyno place this morning to tell them I wouldn't be coming due to 'mechanical problems'. They said no problem, but why didn't I come down on Saturday anyway as they were having an open day and dyno runs were free

BigD · Post by **BigD** » Sat Jun 04, 2005 12:50 pm

Ok....I've just had the diaphragm off and inspected it and I can't find any splits/tears in it. Will it be obvious? Is there anything else to check with the diaphragm/petcock re fuel in the vac hose?

Help!!!!!!!!!! Put the diaphragm back on and turned the tank over and petrol is pissing out of the hose furthest away from the petcock. Is this cause theres no vacuum now or something? Didn't do it when I disconnected the hose before I removed the tank.

Sorted it. Just clamped the hose until I had reconnected it. I've changed the air filter which looked a bit dirty and was probably due. Off on a test ride

Johnny Wishbone · Post by **Johnny Wishbone** » Tue Jun 07, 2005 9:17 am

Does that mean your sorted or not?? Is there fuel still piddling out of the diaphragm chamber port? You sure there's a spring in there!!??

BigD · Post by **BigD** » Tue Jun 07, 2005 8:57 pm

Hi Johnny, thanks for your continued interest. I've just bought a petcock of Daz which I am picking up from the sorting office tomorrow and will compare the two. Difficult to tell if its still 'piddling' or not as I haven't had chance to put in many miles since I fiddled. There is def a spring in there

In v simplistic terms, what does the diaphragm do? How should it look (apart from the obvious to tears/splits)?

Stormin Ben · Post by **Stormin Ben** » Tue Jun 07, 2005 11:32 pm

BigD
If you're looking to get rid of your old faulty petcock I may be interested in taking it off your hands
Drop me a PM either way

Ben