1990 UK model, 35k miles. always starts first go, accelerates to red line sweet as a button, cruise all day at 5000 rpm but the engine misses and then dies completely after a couple of minutes hard work (eg 80mph up hill) Sloution seems to be pull over, flick fuel tap to 'Prime' ans crank it a few times in that position, flick back over to 'On' and away to go !  I'm almost certain its a fuel starvation problem rather than electrical / mechanical. Cleaned loads of crap out of tank and float bowls, removed an aftermarket in-line filter between fuel tap and carbs, and all fuel lines. Anyone had any similar problems ? There is a plastic T piece connector halfway along the vacuum line between fuel tap and carbs - is this normal or should it just be a contiuous  line ?

any help gratefully received - but don't tell me to ride slowly !

hey guys I am the excact same problem, i Just have mine on PRI and Then turn it to On and then Back and works it's weird but works lol, any help would be great.

Pop your gas cap open next time that happens. . .

T in vacuum line ... that's not right. Further You cleaned the tank ... clean the carbs and you have rust in tank ... then the fuel filter needs to be in there ...
Cool.
Srinath.

thanks Srinath
now the tank has sprung a leak !  Have got another one on order from a breakers together with a one piece vacuum pipe so will let you know how I get on !
and I thought my missus was giving me grief !

I have the same problem too, i've had my bike about a month now and there have been a few occasions where i will be cruising quite happily either at high speed (85 mph) or at low speed (30MPH) and i will lose power completely just before the bike stalls as i'm going along, just yesterday it happened on the motorway in the far right lane not good!!! the bike wont start with the patrol tap turned to on, but will with reserve.  I dont understand as the bike had a full tank. Any ideas?

will try my new bits one by one when they arrive to see if they make a difference. I've been told the T piece connector in the vacuum pipe may have been for a Scottoiler which has been taken off the bike but wasn't blanked off so air is getting into the vacuum line. Maybe this is preventing sufficient fuel getting through at high speed ?  Will keep you posted !

Quote from: GS5ukgood!!! the bike wont start with the patrol tap turned to on, but will with reserve.  I dont understand as the bike had a full tank. Any ideas?

When you turn from "ON" to "Reserve" it passes "Prime" and gets some gas to the float bowls.  Suspect that your tank vent is clogged or the vacum hose is bad - could also be a bad diaphram in petcock

Quote from: mjmWhen you turn from "ON" to "Reserve" it passes "Prime" and gets some gas to the float bowls.

Only on the '01+ models.  On earlier models the fuel switch goes from ON (down) through RES (forward) and then to PRI (up).

Well fingers crossed she's going OK now. Put a new one piece vacuum line on between fuel tap (petcock) and carbs - there was a small plastic T piece connector halfway along the old one which wasn't blanked off. (not sure why this had been put in ? used for balancing carbs ?) Anyway, all I can assume is that because it wasn't blanked off and air was getting in, there wasn't sufficient vacuum at high speed to fully open the diaphram in the fuel tap so I was suffering from fuel starvation ?

Thanks for everyone's suggestions.

Quite a bit of mileage covered over weekend and all ok so hopefully problem sorted !  Thanks for advice Srinath