Kinky Fuel Lines

[Tirpitz]

I noticed a problem with my fuel line the other day which, whilst not causing me any obvious issues, could result in some hard to trace poor running in future. I thought I’d flag this up for others to check too.

The routing of the fuel hose from the filter near the pump is a sharp bend to the vertical, before then slowly bending to the rear of the bike and travelling upwards and levelling out to connect with the fuel tap. There isn’t much room between the end of the fuel filter and the frame so the hose tends to rest on the frame during its bend. At this point a kink had developed in the fuel line and whilst flow was still happening the diameter of the pipe was considerably reduced.

I tried re-routing the pipe with no success. Shortening it made matters worse as it was then straining on the fuel tap and likely to work free over time.

I decided to buy a considerably longer section of new hose, about a foot long. This was then routed as follows – from the fuel filter a gentle bend in the horizontal towards the front of the bike, then a bend to the vertical and looping round to the horizontal to pass back to the fuel tap. This route eliminates the tight bend between fuel filter and frame and eliminates the tendency to kink.

I should point out that the hose that kinked was new. If you have old, hard hoses they may not kink (but you should be renewing them if they are years old and hard anyway). Or they may have hardened with a kink. The new hose cost £1.50 so this is a cheap fix which takes minutes, and also helps in future when carb balancing and needing to feed from the tank with it removed. IMO the standard length and routing of the fuel hose by Kawasaki is a design fault which could result in fuel starvation with prolonged operation at wide throttle openings. Maybe not so noticeable on public roads but a track day might bring a few glitches.

[Big Al]

Had the same problem but found that all after market fuel lines kinked.The OEM pipe is pre-formed to fit and i must admit that i have not had any problems with it kinking / fuel starvation etc and i have been on several track days since changing it. Just a quick question, have you got an after market or original fuel filter fitted? and is it fitted in it clamp? I had trouble finding one but eventually took my old one into a local bike shop who matched it to a YAMAHA! component (identical ) This really did improve running especially at full throttle. Nothing personal, but what makes you think the Kawasaki design is at fault? The lines are kept short and there is plenty of head pressure from the tank to the pump inlet (engineer). Have read others make the same observation about poor fuel system design but no technical argument to back it up. Have i just opened a can o worms?

[Tirpitz]

It's a good point about aftermarket versus OEM stuff. My lines are aftermarket as I restored the bike to the road after a 13 year lay-up. Fuel lines were old and hard, and Kwak anyway recommend replacement after 4 years (but I bet very few people do it!).

The fuel filter is the original and is in OEM clamp.

I take back all I said about Kwak's poor design. Sounds like this is a case of if you replace the hoses with OEM you won't have a problem but if you use aftermarket hose you might want to reroute the hose to 'cure' the problem you are going to introduce.