Engine buggered

[ChristoT]

Hi all,

Looks like the ZX-4 engine has bitten the dust. I was cruising up the A303 (from Portsmouth, originally), having only just hit the Andover slip road when the coolant gauge shot to the red like a rocket (as fast as the tacho, when you blip the throttle with the clutch in!), before can-can-ing around, and finally sticking resolutely bang in the middle of the dial (this was at just under 70). Also, a frightful knocking sound then came from the engine, as if someone was hitting a heavy frying pan with a hammer - hard. When the RAC patrol car arrived, he also detected water in the oil.

The RAC chap reckons it's a piston ring, the mechanic at the bike shop I go to where the RAC dropped me off (on a 14t lorry, looked ridiculous!) reckons the water pump has gone south. Either way, it ain't good.

My question is this: what engine parts are compatible with the ZXR? This is a 1988 ZX-400G, and as it is one of the very first, I want to repair it.

Any other ideas as to what it may be to cheer me up?

Cheers!

[Ewetea]

I can think of a number of things that could have gone wrong, but the best solution to the problem is to start dismantling parts. The water pump is held in place by two long bolts, with two more short bolts securing the cover. Remove them and take the cover off. Maybe the water circulator has detached from the shaft. If that is the case, it is easy enough to replace the complete assembly. If everything is sound, then you'll have to investigate the top end of the engine. Check the compressions on each cylinder. If you don't have a tester, you will have to improvise - a piece of rod with a rag on the end held firmly on the spark plug hole. It's crude, but if a ring has gone then there may be a noticeable difference in the force necessary to hold the rod in place. Take the carbs off and peer down the ports to check that all valves are in place. After that, I can only suggest that the head and barrels are removed. That will enable you to check the piston rings and also peer in the crankcase to see if anything is loose - maybe a big end bolt floating around?!! The best way to dismantle the engine is to drop it out of the frame...so you're going to be busy. I'm sure that parts can be sourced by an appeal on the zxrworld website - photos of what you require would be the best way to ensure you get what you want. Look on the exercise as a winter overhaul.

[ChristoT]

I can think of a number of things that could have gone wrong, but the best solution to the problem is to start dismantling parts. The water pump is held in place by two long bolts, with two more short bolts securing the cover. Remove them and take the cover off. Maybe the water circulator has detached from the shaft. If that is the case, it is easy enough to replace the complete assembly. If everything is sound, then you'll have to investigate the top end of the engine. Check the compressions on each cylinder. If you don't have a tester, you will have to improvise - a piece of rod with a rag on the end held firmly on the spark plug hole. It's crude, but if a ring has gone then there may be a noticeable difference in the force necessary to hold the rod in place. Take the carbs off and peer down the ports to check that all valves are in place. After that, I can only suggest that the head and barrels are removed. That will enable you to check the piston rings and also peer in the crankcase to see if anything is loose - maybe a big end bolt floating around?!! The best way to dismantle the engine is to drop it out of the frame...so you're going to be busy. I'm sure that parts can be sourced by an appeal on the zxrworld website - photos of what you require would be the best way to ensure you get what you want. Look on the exercise as a winter overhaul.

Well, I'm waiting for a diagnosis from the garage (my bike is currently 75 odd miles away!), but if it's going to be over budget, and I can't see how it WON'T, then a major restoration is on the cards.

At least my parents are lending me enough money to buy a little car in the meantime...

[Vaughn]

I have 2 engines worth of spares including 2 water pumps and 8 pistons with rings,
if you need anything let me know

[ChristoT]

I have 2 engines worth of spares including 2 water pumps and 8 pistons with rings,
if you need anything let me know

If those will fit a ZX-4, I shall certainly take you up on those! Thanks!

[Vaughn]

If those will fit a ZX-4, I shall certainly take you up on those! Thanks!

I really don't know but i suspect it might fit, loads here if you need anything just let me know

[ChristoT]

If those will fit a ZX-4, I shall certainly take you up on those! Thanks!

I really don't know but i suspect it might fit, loads here if you need anything just let me know

Will do, ta!

[banner001]

if a zxr400 engine will fit it might be simpler to just swap the engines, you are looking at £300 for a decent zxr400 engine, and probably close to £600 for a full rebuild.

if there is a little water in the oil i reckon at the very least you have blown the head gasket, if it was a lot of water you might have cracked a barrel or something equally serious...and probably engine-wrecking.

if you have broken a ring you might be able to get away with re-honing the bore (if its not gouged it) and fitting new rings, failing that it would be re-bore and over sized pistons or replacement barrels.

[stuzx4r]

Hi, a zxr engine will bolt straight into a zx4, however you do need to use the ignition pickup from your old zx4 engine.

Good luck, Stuart.

[ChristoT]

Quick update:

Well, turns out there was hardly any water in the oil - good start! However, the bike got so hot, the nipple on the header tank plastic welded itself shut! So now, it's time for the strip and check everything. The thing that worries me is that when you open the rad top, there's a horrible burnt smell. The fan has half melted, and is now revolvong eccentically. First think I'll do when I pull the engine is check the oil/coolant pump. According to the mechanic who replaced some seals on it a few months ago, both liquids are drived by (basically) the same pump - obviously sealed so they can't mix. That's my first port of call.

The worry with the heat is that the engine may have dropped a liner. I have no idea how repairable (if at all) that is.

[Mori Man]

If the pump has crumbled you'll be into a full strip down to find all the bits as they will trapped through out your cooling system.

Likely had a partial seizure at high temp - sometimes you get away with that but your best checking your piston skirts for damage.

If you can get a known working ZXR engine that could likely be your cheapest fix.

[ChristoT]

If the pump has crumbled you'll be into a full strip down to find all the bits as they will trapped through out your cooling system.

Likely had a partial seizure at high temp - sometimes you get away with that but your best checking your piston skirts for damage.

If you can get a known working ZXR engine that could likely be your cheapest fix.

The engine kept turning, but made a horrific knocking sound - and lost a lot of power. A full strip was always on the cards, so continuing with that. Slightly concerned about the radiator - if the header was anything to go by, it'll be filled with horrible red gunge! Any advice on cleaning that crap out?

Do you know of a ZXR engine for sale for circa £100?

[Mori Man]

At high temps all service limits on parts go way out - hence lots of knocking noises.

Stripping a motor down isn't as daunting as you think , it's having the space as ideally you want lay things out as they are removed and keep in order , box everything as sets so they are placed back in the right order.

Me I just shove everything into tubs as I have built a few engines in my time but valve sets are still numbered as are pistons to cylinders.

If you go full strip and rebuild give me a shout as an overhaul kit will be way cheaper from here

If the bike is going to be a keeper or long tern user then consider a full refresh with new bearings etc for peace of mind.

[Mori Man]

Rad - i flush out with a garden hose until it runs clear

[ChristoT]

Thanks mori man!

The bike is number 196 of a mere 3,000 ever built - hence my hesitance to chuck it (the sensible solution) rather than rebuild (the stupid, expensive, emotion-driven path I'm taking).