www.zxrworld.co.uk

Just replaced head gasket, put timing back to how it was (same as manual). however it wont start now, and a compression test revealed crazy numbers..

cylinder 1 - 180 psi
cylinder 2 - 185
cylinder 3 - 180
cylinder 3 - 175

this is a pic of the timing before i did the head gasket and ive put everything back to exacly this; (red marks are painted over timing marks)





Anyone help with this please.

Regards

May sound stupid but is everything the right way round? All marks are in the right place with the manual but were the pistons at TDC for pistons 1&4? I'm not taking the piss as when I did my head gasket I put the cams in with the marks facing the wrong way! Nothing hit luckily, I was 16 at the time do cut me some slack after I got everything on the right way mine wouldn't start either, i was using easy start and warming up the plugs and it went, hopefully someone else will be able to explain the massively high compression though?

is the head gasket exactly the same thickness as the one you removed?

if it was fine before, but high now then you must have decreased the volume inside the engine when the piston hits TDC.

inlet and exhaust cams in the right places (i.e. you've not put the 'ex' cam where the 'in' should be?)

Thanks for the help,

Head gasket is oem part from cradleys kawasaki so should be all ok.

as for when piston hits tdc, is it possible that pulsar plate with the timing marks can become out of sync with the crankshaft? so for example when pulsar plate states TDC, the pistons arnt actually at TDC? as now I remember whilst unscrewing the pulsar plate off, the whole thing turnt backwards for a moment, so mabey its now become out-of-sync?

And finnally, i have checked the cams, that was first thing I checked and all was OK

Thanks,

There's a locating pin on the crankshaft when you take the pulsar plate off, unless its bent or the groove is massively worn it shouldn't become out of sync, take the plugs out and see if they're soaked in fuel, when I fecked it up I had 2&3 at tdc and it didn't work, so I would check that its 1&4 at tdc, not sure on the proper method but the way I did it was get a long Philips screwdriver and rest it down in the spark plug hole, then turn the crankshaft and you will be able to easily see when its at tdc, im hoping someone will tell me a better method though

I'm a bit sad sometimes, so for the last 4 hours ive been trying to work out your high cylinder compression, so far my only ideas are;
Valves too tight
Did you clean the carbon of the pistons and head?
Compression tester faulty

ross46 wrote:I'm a bit sad sometimes, so for the last 4 hours ive been trying to work out your high cylinder compression, so far my only ideas are;
Valves too tight
Did you clean the carbon of the pistons and head?
Compression tester faulty

its odd, because reading the OP's previous posts he used the compression tester not so long ago, and he hasnt mentioned messing about with the valves. im doubtfull that he could do that many miles on the bike that it would foul with carbon so much that his two readings before/after the gasket, could be so out.

the HG on the zxr (im still to remove mine) is it a single gasket, or is it like my fzr 1000 where its 3 gaskets stacked on top of each other?

there is a chance that someone was running with 2 stacked gaskets, and you have removed these and just replaced it with a single gasket?

also did you do both readings (before and after HG swap) with a warm engine, or is this a cold reading (i suppose if you cant start it it must be...).

even if the pulsar plate had shifted it wouldnt affect your compression, just your spark timing.

is it possible (ask moriman) that your bike has the SP's high-comp pistons? in which case 180psi is about right and you will need to run ~98RON fuel, so thats uk premium fuel, it will knock with 95RON most likely.

also have you checked with a flashlight etc that you dont have water/coolant/liquid petrol/oil in the combustion chamber as these will all lead to high compression readings...

also, make sure that you hold the throttle wide open when doing compression tests...

So its not going to be the tester, normal readings before and not now, the carbon build up was out of the manual and your right banner carbon will not have built up that quickly and same for the valves, my last theory was oil/coolant but I omitted that as he's just done the hg and got all the timing right which I personally think is the most difficult bit. Did you do the head bolts up in the right order? Hopefully moriman will be able to shed some light about high compression pistons. To the poster about your starting issues, what made you change the head gasket? have you checked air, fuel and spark?

Firstly, thanks so much for all the replies.

I changed the head gasket as i had head gasket symptoms, including leaking cooling fluid into combustion chamber, getting hot quick ect. The head gasket that i took off the bike was a single head gasket. I can confirm this fixed the leak. I took a compression test a while a go (when running OK) and measured all around 130, i knew somthing was different this time as the starter sounded different when turning the engine, then took compression test and it said all around 180. This was with a cold engine, with the carbs off and all plugs out.

I havent touched the valves. havent even measured them as my feeler gauge has gone walkies somwhere, however the engine was operating fine before. When i set the timing, piston 1 & 4 was at TDC and 2,3 were at the bottom. there was carbon build up but a tiny layer. see below pic of build up on pistons and also the blown gasket.

Really need to get this running soon as I had my first track day booked for 3 weeks time, dont wana miss it!

ross46 wrote:So its not going to be the tester, normal readings before and not now, the carbon build up was out of the manual and your right banner carbon will not have built up that quickly and same for the valves, my last theory was oil/coolant but I omitted that as he's just done the hg and got all the timing right which I personally think is the most difficult bit. Did you do the head bolts up in the right order? Hopefully moriman will be able to shed some light about high compression pistons. To the poster about your starting issues, what made you change the head gasket? have you checked air, fuel and spark?

Ross, you mentioned doing the head bolts up in the right order; can you explain the importance of this? i remember reading and slowly tightening in a zig-zag

Page 14, top end chapter of the H manual, as far as I can remember its to make sure that the gasket is compressed fully and the head goes on square, if the head didn't then you could have an internal leak which could put oil in the cylinders causing higher compression, but im not sure as all 4 cylinders are high?

Did you manage to find the problem mate? Has the head been skimmed and/or the base gasket removed? you got it started yet?