748 rebuild - where the chuff do these connect?

Exige

2021 Build of the year winner
Subscriber
Will give it a whack tomorrow whilst powering it up. If all else fails I'll drop you a message
It will probably work, gave my zero mile 1999 R6 pump a tap when recommissioning it to sell the other month and it instantly whirred into action - that's after having only started once 10 years ago in it's 22 year life.
If it has sat with fuel in be prepared to flush it through with a gravity fed tube / funnel if it spins.
 

Keith_henson

Member
Subscriber
It will probably work, gave my zero mile 1999 R6 pump a tap when recommissioning it to sell the other month and it instantly whirred into action - that's after having only started once 10 years ago in it's 22 year life.
If it has sat with fuel in be prepared to flush it through with a gravity fed tube / funnel if it spins.
OK, tried powering it up and giving it a whack a few times with a wooden mallet to no avail. It still will not prime. Is it worth leaving it in fresh fuel to try and ease it up? or some other cleaner/lubricant to clean it out? Any thoughts would be welcome before I hit buy it now on ebay for a new replacement one.

Many thanks

Keith

P.S. I have yet to put a multi meter across the 12v poles on the wiring as a just in case there is a deeper, darker issue, thats a job for tomorrow
 

Exige

2021 Build of the year winner
Subscriber
OK, tried powering it up and giving it a whack a few times with a wooden mallet to no avail. It still will not prime. Is it worth leaving it in fresh fuel to try and ease it up? or some other cleaner/lubricant to clean it out? Any thoughts would be welcome before I hit buy it now on ebay for a new replacement one.

Many thanks

Keith

P.S. I have yet to put a multi meter across the 12v poles on the wiring as a just in case there is a deeper, darker issue, thats a job for tomorrow
I was just going to say have you removed it and powered it direct from a battery to make sure it's the fuel pump is stuck :unsure:
 

Barry Hell

Elite Member
Subscriber
OK, tried powering it up and giving it a whack a few times with a wooden mallet to no avail. It still will not prime. Is it worth leaving it in fresh fuel to try and ease it up? or some other cleaner/lubricant to clean it out? Any thoughts would be welcome before I hit buy it now on ebay for a new replacement one.

Many thanks

Keith

P.S. I have yet to put a multi meter across the 12v poles on the wiring as a just in case there is a deeper, darker issue, thats a job for tomorrow
Carb cleaner 👍 may help ease it if stuck
 

Keith_henson

Member
Subscriber
News update. Pump works fine across 12v battery terminals direct. Reconnected the assembly to the bike and no priming noise.

It seems to be a wiring/immobiliser gremlin which is a bit beyond my skills. Looks like it's time to deliver it to the experts at the local bike garage to hunt it down for me (whilst I vanish to Saudi and UAE over the next three weeks).

So close but so far 😔
 

West Cork Paul

Shed Expert
Subscriber
News update. Pump works fine across 12v battery terminals direct. Reconnected the assembly to the bike and no priming noise.

It seems to be a wiring/immobiliser gremlin which is a bit beyond my skills. Looks like it's time to deliver it to the experts at the local bike garage to hunt it down for me (whilst I vanish to Saudi and UAE over the next three weeks).

So close but so far 😔
There’s no immobiliser on these other than what’s added as an after market alarm which you’ve had removed and has the bike running since iirc.

Just a thought. Have you tried bridging the two black wires that went to/from the alarm LED? It could be, on the off-chance, the alarm immobiliser circuit which was bridged when the alarm (but not all it’s wiring) was removed needs a complete circuit to maintain continuity and the LED no longer being connected is breaking it. For the sake of a paper clip and 5mins it’s worth trying. Otherwise it’s out with the multimeter and tracing the fuel pump circuit from battery to earth.
 

Keith_henson

Member
Subscriber
There’s no immobiliser on these other than what’s added as an after market alarm which you’ve had removed and has the bike running since iirc.

Just a thought. Have you tried bridging the two black wires that went to/from the alarm LED? It could be, on the off-chance, the alarm immobiliser circuit which was bridged when the alarm (but not all it’s wiring) was removed needs a complete circuit to maintain continuity and the LED no longer being connected is breaking it. For the sake of a paper clip and 5mins it’s worth trying. Otherwise it’s out with the multimeter and tracing the fuel pump circuit from battery to earth.
I shall give that a look tomorrow. I was speaking to my Pa earlier (an avid collector of velocette's, singles and boxer LE's) and after a half hour on facetime we both think its where the datatag alarm was taken out, maybe when I removed the loom it broke a connection that was made.

Try and try again they say.

Also, the wire diagram in Haynes for my "2001" does not fit. All the wires are totally different colours. It's more a 1996 loom, but then the colours of the wires don't match.

I will crack the problem, with a bloody large hammer if needs be 😂
 

Keith_henson

Member
Subscriber
After muchos thoughts and speaking to my mate Jay this savvo who runs Road and Race in Telford (with multiple cups of tea), we may have stumbled upon the issue. Where the alarm was taken out, is also where the rear brake wires run into. Neither are working, which suggests I have damaged an earth that has been re-connected after the alarm removal during faffing to get the loom to fit correctly after the frame re-spray.

Lunch break tomorrow is to run an earth direct from the fuel pump assembly ground to the battery then turn it over. Fingers crossed this will work and the loom just needs the protective tape taking off and finding the connection issue. If not, then Jay can just keep it, fix it, MOT it and I'll just ride it :D

He is going to Dyno it so I can see how my old girl behaves. I replaced the stock exhausts with 50mm carbon termis and have the standard chip and a race eprom chip for the 50mm pipes. He's going to do a run on both chips and I'll post results here (after I get the fuel pump working!)

Alas, Saudi and UAE are calling on Thursday for a few weeks so I hope I get it running!
 
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