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Piston gone!

b wizzQ: I’ve had my BWS for five years now with no problems at all and, it’s still the best scooter ever made, even though Yamaha has stopped making them now.

Recently a ‘pop’ noise came from the engine and it locked the back wheel, which obviously means it’s seized! I had no idea why until I discovered the main jet was blocked with some sticky stuff, which is congealed fuel, I presume.

So I took off the head and barrel to discover the piston had a hole in it but the crankshaft assembly was covered and sprayed in aluminium debris, great!

The reason I’m writing is, I’ve asked many people how, or should I, clean out this mess. Some say just wash it out with petrol and rebuild the top end, others say split the crankcases and rebuilt the entire motor with new bearings and con-rod assembly. So what do you recommend?

Stuart.

A: We’ve seen riders blow up these engines whilst racing, and they just wash the engine out with petrol and ‘stick’ a new piston in, which isn’t really ideal for longevity.

If you use it a lot one way is to take out the whole rear end/engine and wash the engine/crankcase out with paraffin. We’d recommend removing the two crank seals and fitting new ones afterwards so you can get inside the bearings and finally wash out with petrol. Keep doing this until no debris comes out and rebuild with new parts and gaskets, then you should be good to go.

Knock, knock!

1999 Kawasaki ZX-6RQ: Hi guys. I own a 1999 Kawasaki ZX-6R that is now sitting with 65,000km on the clocks. I’ve had it for over seven years now and it’s never given me any problems at all and it gets serviced at the correct intervals. Mainly because I can’t afford a new ZX-10 and it’s my only form of transport to get to work and play with at the weekends. Hopefully I’ll win the lottery soon and have a new ZX-10RR in my garage!

My reason for writing this though is that I recently went on a long run with my friends and did a spot of top speed dicing, which was great until the next day. When I started the bike I could hear a knocking noise coming from the engine but I’m not really sure where it’s from. I had to ride the bike to work, I have no choice, and the noise didn’t get any worse and did not affect the performance.

So, I’m afraid to ask, but do you have any ideas on what is wrong and, I’m not too keen to strip the motor etc? Any advice will be superb and thanks again.

Mike.

A; I’m afraid it’s very bad news Mike! It’s either the small-end bearing on the piston side or, more than likely the big-end bearing on the crankshaft. These bikes/model are quite prone to this with high mileage and constant high revving.

You WILL have to strip the motor and remove the crankshaft to inspect it correctly, and check the piston pin and it’s bearing as well. If you keep riding it will eventually throw a ‘rod’ out of the motor and destroy the entire engine.

So either go for the repair after pricing, or try and source another engine? Preferably from a bike that’s been crashed, why you ask? Well the engine was obviously running at the time of the accident so you know it works, hopefully not with the same problem though.

Fork it... ZX10!

2008 zx 10Q: I recently changed the fork oil on my 2008 Kawasaki ZX-10 to save time and money on expensive dealer workshop costs.

It’s covered just over 30,000 km now and they (forks) started to feel a bit ‘wooden’ and I can’t even remember when they last received any form of attention. After taking them out and hanging upside down to remove the old stuff, which was black, smelly and vile, I then filled them with the correct recommended weight Motul oil (lightweight).

But, after refitting them and riding they felt exactly the same and nothing like they should. Shouldn’t they work properly again after an oil change, I would like to think so? So, any advice on what to look for would be appreciated?

Many thanks for your time.

Martin Woodbourne.

A: After that many kilometers with little or no attention the forks will definitely have built up residual sludge/paste inside. This will contaminate and block the very small holes and shim stacks that form part of the ZX-10’s damping abilities, which will make the forks feel ‘wooden’ like you’ve said. It will not come out just by turning the forks upside down.

You’ll have to take the forks out again and have someone who’s competent with suspension to strip, clean and rebuild the entire fork internals. And while you’re doing that replace all of the seals as well to save time and possible problems in the future.

Once done we’re sure the forks on your ZX-10 will once more function like they are new items.

Chewy.

1981 GS1000GQ: My father and myself have recently acquired a 1981 Suzuki GS1000G, the one with the shaft drive.

We bought it to do some team bonding and work on it together until it’s ready to be ridden on the road again. It does need a lot of cosmetic work but that’s our problem and the easy side of the story.

The problem, and why we’re asking you knowledgeable guys, is inside the cam cover. We took it off to have a look around and noticed the cam chain has chewed away at the rear top of the cover quite badly. But when we try to pull the chain off the sprocket it doesn’t move very far, certainly not enough to cause this ‘chewing’ effect.

So what should we be looking for and what should we replace before even contemplating to start the engine? The bike has 84,000km on the clock by the way.

Richard and Colin.

A: You’ll be glad to know this is quite an easy fix if you’re a competent mechanic. Basically, the cam chain is well past its life span. When the engine is revved it will ‘leave’ the sprocket due to stretching and therefore touch the top of the cam cover.

Please just check that the cam chain tensioner is working correctly as well. If it isn’t taking up the slack it will have to be replaced because it’s not a serviceable item I’m afraid. If you’re not sure how to check this go onto the Internet and download the workshop manual for your bike, which is easy to perform.

As for the cam chain, new one’s can be bought with a split-link so you don’t have to remove the crankshaft to replace it. Just check (twice) that you still have the correct settings for the camshafts, after installation. These figures can also be found in the workshop manual that I highly recommend you attain before you go any further.

 

 

 

 

 

 

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