Kawasaki GPX750R Spark plugs E10 Fuel and stuff

Published on 10 February 2023 at 15:42

Just been going through all my recently acquired motor cycles to compile a list of what parts I need to buy and what jobs need doing. I started with my 1988 Kawasaki GPX750R, which came in as a non runner. The guy I bought it from said the carbs were over flowing - the oil level was way to high , which is a common indicator that fuel has overflowed from the carbs and found it's way in to the sump. This is always the first check I always do on any carbed bike, it is especially important since the introduction of E10 fuel, which does untold damage to rubber components. Specifically it attacks the rubber diaphragms and o rings in fuel taps and also the rubberised tips on some carb needle valves. The result is often a trashed engine if the petrol dilutes the oil too much and wear is massively accelerated. The other major problem it causes is a hydrolocking of one or more cylinders. A hydrolock is where neat fuel gets in to the combustion chamber, it can't be compressed like air can so it locks the bike engine up. If you then try to start it and it fires on an unlocked cylinder the force when it hits the locked cylinder is huge and it can crack a head or bend a rod.

on the Kwak it's an absolute pain to get at the plugs, lots of bits have to come off to gain access - the middle two plugs are directly under frame members, which makes life especially difficult but it has to be done. 


I always like to check the oil level first and smell the oil - any hint of petrol and it gets drained and gets a new filter before anything else happens. The plugs then come out and the engine gets cranked first by hand and then on the starter. Big word of warning here - disconnect the live from the coils before you do this - usually the easiest way is to pull the ignition fuse. I was too lazy to do this once and when the over fuelled cylinder erupted in a torrent of BP's finest a spark came from the ht lead to ground and my SRAD 600 was engulfed in flames before I could shout even the shortest of expletives. It's up to you whether you follow this advice or not.

Anyway my kwak is locked, no way am I going to spin it on the starter until that's sorted. Sadly some sadist at Kawasaki designed the cylinder head so that no normally sized plug spanner will get in there to get the plugs out. They take a D9AE plug - the d part of that number means it's an 18mm socket required to shift it. My 18mm socket is 26 mm outer diameter, the hole is about 24mm. This is seriously inconvenient, aia tried to fix it by swearing at it but even after an hour and a half of shouted  profanity it still didn't fit. I ordered one on line instead and now have to wait for it to arrive.

In the mean time I will get the carbs off and have a look to see where the problem is, if I don't do that it will just happen again. I know it's not rust in the tank because the inside of the tank looks like new.


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