porndoguk wrote:well it would be better warmer because as metal heats up it swell/expandes so any small gaps that were there cold maynot be there when warm, hence why me and martin have both said test it cold, the haynes isnt always true, there are editing mistakes that a hawk eyed enthusiast will pick up, it also tell you to test the valve clearances on an NC30 wrong too!

Cheers
I only spotted the Haynes mistake on valve clearances after reading the guide on here, mind you I did do clearances on my fazer about 8 years ago so should have noticed, the text was right though.

Probably test the compression before digging the carbs out again to do the float heights, after all if it's buggered I'll have about 12 months to sort it out

oldgreyandslow wrote:

porndoguk wrote:you dont have the engine running for compression testing,

turn the engine over on the starter, with the kill switch OFF and remove all the plugs to make it turn over better.

do it cold as the metal will shrink and youll get a more true reading with the engine warm the metal will expand and mask any leaks etc,

I know it doesn't need to run and to use the kill switch etc I was just questionning the method in Haynes which stated you had to get the engine to operating temp first, I guess the cyclinder compression should be good warm or cold

A compression test on a warm engine may give a slightly higher reading than that of a cold engine as the pistons warm up and expand and prevent so much blow-by... this assumes that the cooling system is working properly and the engine is warmed up to an even temperature.

For your case a cold 'dry' and 'wet' test is all thats needed...

The main thing your concerned with is that the compression in each cylinder is similar.. you'll soon know if you have a problem as one or more cylinders may be dramastically low.

When you add the teaspoon of oil this will help seal the rings temporarily.. so if your compression goes up then you have ring problems... if you still have low compression then you have faulty valves (loosing compression through them) or something worse!

A cold engine max compression might be say 130 when book says 140, this is fine as long as all cylinders are very similar.. this is what were after here.. not absolubte maximum compression.

Hope that helps

PS: Dont' forget.. if your leaving the carbs on make sure you have the throttle pinned 'wide open'

If it's burning that much oil i'd expect to see something 120psi for 3 cylidners and 70 for another..

Neosophist wrote: When you add the teaspoon of oil this will help seal the rings temporarily.. so if your compression goes up then you have ring problems... if you still have low compression then you have faulty valves (loosing compression through them) or something worse!

Lets be optimistic here!

If it is something worse, then the cheapest option is probably a second hand engine

Or strip the bike down and sell whats left for spares and have a bonfire with the remains

Oh and in that situation it'll be kissing goodbye to bikes forever! or getting a divorce

oldgreyandslow wrote:

Neosophist wrote: When you add the teaspoon of oil this will help seal the rings temporarily.. so if your compression goes up then you have ring problems... if you still have low compression then you have faulty valves (loosing compression through them) or something worse!

Lets be optimistic here!

If it is something worse, then the cheapest option is probably a second hand engine

Or strip the bike down and sell whats left for spares and have a bonfire with the remains

Oh and in that situation it'll be kissing goodbye to bikes forever! or getting a divorce

if its rings youd be better off buying another engine anyhow, for the sake of £200 your problems will probally be solved, or get another NC30 and donate the engine over or vice versas, theres a profitable market in breaking bike, even with a fucked engine! theres a runk or parts that could be hand to stacks of people.

steve you seriously need to calm down, we all have our biking dramas its all part of the fun and games they give us before they reward us long term, ive been having carb issues for the last year and im only nearly getting them right, my carbs have been off more times than jodie marshes knickers!

you float height tool has been posted btw

porndoguk wrote: steve you seriously need to calm down, we all have our biking dramas its all part of the fun and games they give us before they reward us long term, ive been having carb issues for the last year and im only nearly getting them right, my carbs have been off more times than jodie marshes knickers!

you float height tool has been posted btw

Cheers Mate for the help and the float height tool too.

This bike was bought as a cheap weekend toy with a view to making some simple and cost effective improvements though not a project! I sold a perfectly good reliable Hornet because I wanted a 400 sportsbike, now why on earth did I do that? Clearly I will have to be patient, take things slowly as and when time and funds allow, however for now I just want to diagnose the problem and then see what my options are.

Tis the major downside to the 400cc market in the UK

Majority of the bikes are getting on for 20+ years old, most have them have been in the UK at least 10 - 15 years now and had many numptys for owners who know little about how to look after / maintain service them.

Combine this with all the replacments you need at that age and they can be quite a lot of money to invest in.

Comming to the end of their life as cheap runarounds... back in the early to mid nineties when they were fresh from japan (who service their bikes a lot better) + they were newer they were a bargain..

all that will be left soon is the high priced ones that are passed between collectors and fewer and fewer sheds each year.

I love the little 400's but i dont have rose tinted glasses and there are loads of other decent bikes out there, sub and greater than 400 class.

Speaking of which.. off to hunt down a set of FCR28's

perhaps I should have gone for that 2000 W plate zxr ............................... shhhhhh mustn't say it too loud

400?

I would have

Loved mine

Don't worry mate, we've all been there. It will reward you soon then all your hard work will have paid off. If you check the compression and there are two adjacent cylinders down on compression (either front two together or rear two together) then the chances are it's just a head gasket.

Let us know how you get on with the testing etc. It'll all pay off in the end

viper61 wrote:Don't worry mate, we've all been there. It will reward you soon then all your hard work will have paid off. If you check the compression and there are two adjacent cylinders down on compression (either front two together or rear two together) then the chances are it's just a head gasket.

Let us know how you get on with the testing etc. It'll all pay off in the end

Thanks "Just" a head gasket sounds OK if you say it quickly enough.

I've borrowed a tester, it is a Gunsons Hi Gauge, my mate has made me an 8mm adapter so tomorrow morning its the BIG test to see if my engine is toast or not.

Qiuestion is: Carbs on or off? If the engines good I'll need to take them off anyway to check float heights, put jets back to standard, if its shagged I'll be taking them off to either get the engine out or do whatever is required to fix it.

Will it make testing easier with carbs off?

I did note the advice above if carbs on pin the throttle open.

Nervous of the result? FFS of course!

Expect a few "Help!!!!" posts tomorrow, or news of a bloke threatening to jump off the top of the multi storey car park in Farnborough!