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Very Enthusiastic Member
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Discussion Starter #1
Hi folks,

Long time no speak (this is on my part btw). Last year I ended up with an M reg Transalp 600 (I still have the RD07). It rode OK, a bit like a pig with the stock suspension etc... but nice enough :) Anyway then I was away with work etc etc life... the bike sat a while. So mid October I decides to start her up, battery flat, recharge sorted. It won't start.. got the tank off, make-shift coke bottle fuel tank, started up eventually, bit lumpy but then sorted itself out. Starts and runs great. Gets the fuel tank back on. Won't start. I check, there is fuel in the fuel hose... Tank off. Now I'm thinking it was bad gone-off petrol.. so drained it the long way... using a syringe on the diaphragm pipe. I double checked it starts fine from the coke bottle fuel tank. Tank back on yesterday... I put a bit of fuel in it, 3-4 glugs of the jerry can. Tap on RES. Starts fine but runs on the fuel that is already in the carbs from the coke bottle tank and then dies. Won't start again... I disconnect the fuel pipe from the tap, there is fuel in there, albeit a dribble. Now the questions:

1. When I pull back on the vacuum pipe with a syringe some petrol comes out then stops. So I have to re-vacuum it. Should this happen? Or should it just stay open? Do I have a dodgy diaphragm?
2. Once the engine us suckin on the vacuum tube, should this be a constant but pulsed pull or on-off / on-off ?
3. Are my carbs not sucking enough? Is using the coke can a red herring as the fuel much more gravity fed ?
4. Or have a simply not put enough fuel in to the tank? The bike is on a paddock stand as-well so not leaning left and low.
5. Could my fuel filter/strained be blocked? (I believe this is in the tank?)

I don't really want to debug the problem by randomly changing parts until it works so any advice/ideas would be much appreciated.

Thanks again and hope all's well around these parts of the world :)
Oli
 

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745 Posts
With the tank on and vacuum hose attached to fuel tap and fuel hose off - when you turn it over on the starter does fuel flow out (catch it in your coke bottle)? Remember to charge battery for your experiments.

If not - are there any splitts on the end of the vacuum hose? trim off a bit for a good airtight seal and apply clip. Check fuel tap diaphram for holes or splits (and while you're poking around in there you can check filter) - replacements here > NRP motorcycle carburettor repair specialist
 

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Hill Rider
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3,089 Posts
Sounds to me like the vacuum diaphragm within the fuel tap is leaking, thus no fuel is constantly flowing out of the carb feed pipe when a vacuum is applied to the fuel tap.

when the engine runs, the vacuum does pusle a bit, but not so much as you'd notice a pulsing fuel supply out of the tap, in my experience.

Taking the tap off of the tank and checking the fuel filter that sticks up from it into the tank will help remove the possability of a blockage at that part of the fuel system.

If you have a vacuum gauge you could attach it to the fuel tap vacuum feed pipe from the carb intake rubber and see how much of a vacuum you are getting. If memory serves me correclty, thats the take off you use when balancing the carbs anyway.

Just my thoughts - it's been a while since I was in the guts of an Alp fuel system - about to change when I strip down the '98 model I've just acquired :D

SteveT

:cool:
 

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A couple of things come to mind...

There are two stubs on the fuel tap that the vac pipe could fit onto but as I recall, only one of the stubs opens the tap with vacuum, this would be the first bit to check & get right.

As Steve says, there is a filter sticking up into the tank, you must remove the tap assembly to access it - note it's position in relation to the tank as the tap needs to align with the hole in the fairing. There is also a fine gauze in the base of the tap (10mm spanner I think).

Test the tap by sucking on a vac pipe attached to the spigot on the tap, fuel should flow when you suck on the pipe when on ON & RES, if when you suck, you need to keep sucking a little bit more and more to maintain vacuum, the diaphragm is probably knackered.


Sent from my SM-A320FL using Tapatalk
 

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Very Enthusiastic Member
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Discussion Starter #7
Ok I disconnected the fuel pipe from the tap turned over a few times as per first suggestion. Fuel pulsates out of the tap, as the vacuum is applied almost a steady stream but more on the visual pulse-ey side. Does the vacuum need to be constant from the hose?

I also had suck on the vac pipe. Fuel flows out OK I didn’t feel like I need to suck more to keep a constant flow (when sucked harder simply more fuel came out). I am almost convinced I have fuel getting down the pipe...but I could be wrong.

Interesting thing is with the make shift tank there is a constant head pressure from the fuel (upside down bottle) and things work fine.

Surely the fuel can’t be getting contaminated to such a bad degree in the tank that it won’t fire would it? I topped up fresh before test this evening.

It might be tank off, air box off and check underneath time. I wonder if the makeshift tank head pressure is just somehow getting the fuel over some obstacle further down the fuel line... I do have a spark btw.
 

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Very Enthusiastic Member
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391 Posts
Discussion Starter #8
Ha! I’m an idiot. Thanking everyone for all the advice with regards to eliminating possible culprits. Basically I have just put my drained crap fuel back in to the tank AGAIN and that was the reason for no run. DOH!!! Starts and runs fine now after another quick drain and real clean fuel. Blooming Jerry cans looking the same. All I need now is a front brake switch and I should be MOT ready! Thanks again Oli
 

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Hill Rider
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3,089 Posts
Glad your sorted :thumbup:

Started onto the strip down of my '98 Alp - seems to me that nearly every bolt I remove hasn't been interfered with since it was fitted at manufacture :D

Steve T

:cool:
 
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