Flames, Glowing exahst, Backfiring

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paton

paton

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Ok first off, I did the valve clearances a couple of weeks ago with a strange result, not much compression came back if anything it got worse:confused: Bike still ran and started ok. I also changed my plug at this time (NGK CS7HSA)

I'm sure i did them right as i checked them 3 times when i got this strange result.

After two 3 hour sessions at the track on the weekend i start the bike up today in the shed, no probs. But then realize the pipe was glowing at the head, and when i gave it a rev it was like bad special effects from the first terminator movie with flames shooting a good 10 inches out of the zorst as the revs wound down.

It backfires a heap and it even backfired a couple of times out the air filter.

I will start will doing the valves tomorrow after work, as clearly the motor it too hot to do them now, and give the carb a clean. I did a bit of a search and found that it could also be an air leak at the header???

I really hope i don't have a bent valve cause i aint have a clue how too change them.

Will this solve my problems or has the Z finally given up?

Engine: 155z
Carb: Mikuni 30mm (fake)
Exhaust: Stock Dpro 160

Thanks guys.
 
if you set the valves on the wrong TDC that's what you'll get, do you make 100% sure you're on the compression stroke before setting them?

could be an air leak in the intake side but I doubt it sounds like you've stuffed up the valve clearance, topguntravis did the same thing last time we were at parwan and his engine overheated like crazy
 
hmm yeh rip i always make sure I'm at the top of TDC by watching the valves open and close to see that it's at the top of the compression stroke making sure I'm not on valve overlap. I even checked it with small screw driver if i remember rightly.

I'll have another go at the valves tommorow i must have f'ed it up i cant see it being anything else. i haven't changed anything else except for the spark plug
 
It's also possible that you shifted the valve slightly while (or after) adjusting it...
 
^^ can you elaborate for us? does that just mean i knocked the valve? how would i go about fixing it if i had?
 
ummm so you watch the valves? how you mean? if you rock the flywheel at TDC do the valves move?
 
^^^Thanks Krazed im sure ive read it but ill have another flick through it.

As in when i turn the flywheel watching the rocker arms go up on the intake stroke then both closed on the top of the compression. And yes i also check by rocking the flywheel with no valve movement on TDC
 
No probs... Hopefully this solves your problem, although you aren't the first. Perhaps look into whether it is running too lean too :)
 
easiest way is to remove the cam cover... cam gear dot @ 9 o'clock ...no guess work then...

just in case you didnt know too, the piston goes to the top twice in 1 cycle of the valves...
once is the real tdc
the other is where the valves will rock (exhaust shuts and inlet opens)

so checking with a screw driver can be misleading...
 
sorry no crf, i would start it up and get a vid of me lighting the barbie or a bonfire with it but im a bit worried it may do more damage ;)

Thanks sean, I am positive i am getting TDC as the valves dont rock like false TDC. Will have another go i must have buggered it even tho i am certain of the theory behind it.
 
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Right went back out to the shed. Motor is cold to touch but prob not 100% Anyway


1. Removed all cam covers, flywheel cover, inspection covers.

2. Rotated flywheel untill both "T" on flywheel and Arrow on Cam Line up at 12 and 9 o'clock respectivly.

3 Rocked the flywheel, No movement from rockers. Did a 360 found false TDC, did another 360 back to TDC

4. Got the feelers out, inlet is tight as a nuns cant even get a .001 in there and the exhaust is somewhere between .002 and .003

5. Slapped head realized i must have f'ed it.

Will reset the clearances tomorrow when i know the motor is stone cold.

Thanks for the help fellas
 
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Oh snap... Now that it's nice and dark, get that vid for us! ;)

Least you'll have it sorted tomorrow!
 
Ok fellas, now i did my valves correctly this time (took my time) and found all my compression came back... exellent :D

Started the second kick and let it warm up a couple of minutes.
Gave it a few revs (slight) nothing appears wrong.
Gave it a few hard revs and thought i heard a backfire, then look down and the zorst is starting to go a red color... another rev and sure enough flame on, any one for a ciggie?

The only other thing i noticed was my inlet valve inspection caps o-ring is broken. Could this cause it not to seal properly and somehow let unwanted air in?

Otherwise where should i got from here? It runs, idels, has a shitload of compression again.
 
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