Diagnostic mystery.. (to me anyway)

[Danman109]

Hey all,

So iv just purchased a new L2 after my accident, immediately after picking the bike up i knew it had issues, no problem im up for a challenge..

It sounds very rough and lumpy, like its running alternately on 3 then 4 cylinders (sorta sounds like a V twin while pulling away down on power too) it leaks coolant after/during a ride, not excessively but a few drips at a time when hot. After an hours ride with friends it overheated, however I rode it 110 miles home it didn't overheat once.

Things checked/replaced so far:

New HT leads
New Iridium plugs
Redex'd a tank of fuel,
Checked all the carb diaphragms are sitting correctly,
Checked mixture screws 1 3/4 turn out
Balanced the carbs,

I'm leaning towards the idea that its head gasket and its attempting to run on a coolant/fuel mixture on one cylinder... but im open to ANY other ideas before going down that route!

How would I be certain its head gasket before going ahead?

Much obliged as always! I loved and missed my beloved 400 so much after my accident I got another! love 'em! wont rest untill this one is as good, if not better than my old one!

Dan

[thomp1983]

if your certain you can't find any external leaks to account for the drips of coolant when then id be looking at a compression test next

chris

[EvilSpike]

+1 on the compression test, that should show you if one cylinder has got a leak in the head somewhere.

Any mayo in the oil?

Don't suppose it could be just a massive airlock in the cooling system?

[Danman109]

+1 on the compression test, that should show you if one cylinder has got a leak in the head somewhere.

Any mayo in the oil?

Don't suppose it could be just a massive airlock in the cooling system?

Running the bike with the rad cap off makes bubbles come out.. i thought we'd got them all out but theyre back. Bike gurgles just after you switch it off but theres no mayo in the oil.

I'll see what i can do about getting a compression test Thanks!

[RedexRobB]

Whats it like temperature wise?

[Danman109]

Whats it like temperature wise?

I've never had a problem untill this one ride out on country lanes doing 60-70 testing out the bike for about an hour and when i got back the temp was above the 3/4 red line when the fan normally kicks in.. :-S

the fan does work, iv had it working before (its possible its not working now) but having just stopped it shouldnt be that hot? But it has got bubbles in the coolant system even though we bled the system last weekend..

I feel like a kid who's favourite toy has broken, iv thrown a tantrum and left it in the garage!

[RedexRobB]

All points to a headgasket for me, but a compression test will probably confirm it. Also i wouldnt ride it till you have sorted it.

[Danman109]

All points to a headgasket for me, but a compression test will probably confirm it. Also i wouldnt ride it till you have sorted it.

Thanks Rob, is the head gasket a possible cause for it sounding like a tractor?

before the overheating problem i thought it might be carbs and was going to take it to a dyno to get them sorted.. :/

not riding it is gonna be painful! lucky i dont need to commute on it.. yet..

[Tirpitz]

All points to a headgasket for me, but a compression test will probably confirm it. Also i wouldnt ride it till you have sorted it.

.....I'm afraid

When you get inside for the HG change you may find other nasties which could account for the rough running.

[Mori Man]

Head gasket blowing internally , one cylinder may be having the spark blown out so miss fires , if regular you should get some back fire or a bang on start up with unspent fuel in the system.

Good opportunity to give it a right good service although I can see you'd be rather using it - me too, hate having to pull the bike off the road to work on it

Got to get the 2nd one built to tackle all those nigglies on the first That's what I am telling the wife anyways

MM!

PS. consider having the head skimmed (mild) , dress the ports and lap the valves in - going to give you a smooth running motor

[Danman109]

Head gasket blowing internally , one cylinder may be having the spark blown out so miss fires , if regular you should get some back fire or a bang on start up with unspent fuel in the system.

Good opportunity to give it a right good service although I can see you'd be rather using it - me too, hate having to pull the bike off the road to work on it

Got to get the 2nd one built to tackle all those nigglies on the first That's what I am telling the wife anyways

MM!

PS. consider having the head skimmed (mild) , dress the ports and lap the valves in - going to give you a smooth running motor

Thanks MM!

yes i was dreading the realisation that it was the HG it doesnt back fire though..

Need to hassle the insurance company to get my salvage back so i can drop the old engine in while i change the HG on this engine!

iv never skimmed the head, or dressed the ports? or lap the valves in? (learning new things here)

I was hoping to tune the old engine this christmas to drop it into the new bike for the new season, no chance now :/ this winter is gonna be tough! iv got a hire bike but its no zxr400 and no guarantees how long iv got it for

Thanks again

Dan

[Danman109]

Was at the garage last night,

The fan on the bike does work, it kicks in a little earlier than the L9, maybe a fraction over half way (no bad thing?) its taken a bit of coolant out of the expansion tank but nothing drastic. So i decided to take it for a ride.

I rode it for about an hour and a half at deliberately high rpm's to mimic the hard riding that caused it to overheat before... but nothing.. it ran slightly hotter than my L9 (but i was in 1st around town most of the time, like the obnoxious sport bike rider i am ) but no over heating do we still think head gasket? still sounds like a tractor and underpowered though!

The new gasket is on its way but i'll be mad at myself for attempting to fix something that aint broke!

Any ideas?

[Mori Man]

Your coolant system being pressurized points to an internal head gasket leak or warped head & both.
Bubbles do not occur naturaly in the system only after a refile and purging the system.
Fan coming on early also indicates the thermostat has an air bubble but thermo sensor is detecting the rad' overheating - that's why it's a failsafe device until it fails
Fans that come on from the thermostat sensor are always a bad thing as thermostats are mechanical and can fail plus air bubbles being traped in the chamber will show the bike running cooler than it actually is.
Like all things , there are good n bad days - don't take it as you've cured it by one good ride !

Do you feel confident to ride every day without failure ? If so then you got lucky and do it - but me, I would be off with it's head

MM!

[Danman109]

Your coolant system being pressurized points to an internal head gasket leak or warped head & both.
Bubbles do not occur naturaly in the system only after a refile and purging the system.
Fan coming on early also indicates the thermostat has an air bubble but thermo sensor is detecting the rad' overheating - that's why it's a failsafe device until it fails
Fans that come on from the thermostat sensor are always a bad thing as thermostats are mechanical and can fail plus air bubbles being traped in the chamber will show the bike running cooler than it actually is.
Like all things , there are good n bad days - don't take it as you've cured it by one good ride !

Do you feel confident to ride every day without failure ? If so then you got lucky and do it - but me, I would be off with it's head

MM!

So iv just seen the list of things to do if i wanted to change the head gasket myself...

iv bought the new HG from Cradley, £18 Next day it arrived.. (love that!)

however i have bigger questions like cam chain tools.. how much are they and where can i get them from? Im seriously doubting i can manage to do this myself, its annoying because im happy to strip the motor out, but then i'd need to take it somewhere to get it done...

Im reluctant to spend big bucks to pay someone to take apart the bike, when i can do that part myself..

[Mori Man]

Think your freakin over nothing

Look at the workshop manual on the front page of the site , search threads on valve timing and shim swap

No special tools needed.

Remove pulsar cover, remove cam cover , 8&10mm socket

Set valve timing to #1 TDC 17mm spanner

remove camcaps in accordance to manual 10mm socket

remove chain guides 5mm allen key needed

remove head nuts 12mm socket, remove head

rebuild opposite way.

No special tools required.

Checking your shims you need a micrometer and feeler gauges and you as well doing as part of this job but you can just replace the gasket and ignore everything else - your call.