Fao: Bikers!

Post by **Tumble** » Wed May 09, 2007 6:34 pm

Hippy wrote: Well, discovered the reason why i'm finding the bike underpowered, it's blown it's head gasket!
Hey, this is just like owning a classic car!
Oh well, at least on the bike it's a Â£5 20 minute job.

There's them famous last words

Post by **Dangerous Bob** » Wed May 09, 2007 10:41 pm

aaahhh..

I'replaced many a head gasket on smaller bikes with a weetabix box job and some hylomar......

Post by **Hippy** » Thu May 10, 2007 10:08 am

Lol, well i though't i'd splash out and get a proper gasket.
Save the weetabix boxes for the triumph

Post by **andrew** » Thu May 10, 2007 6:14 pm

Might have finally sourced myself a minter, bit overpriced at the moment but working on that issue alongside beating everyone else to it !

Post by **Hippy** » Tue May 15, 2007 9:20 am

Right, need some help on this bike.

Took the head off, gasket was fine, de-coked the piston and head, cleaned the surfaces, replaced with new gasket, cleaned the spark plug surface. Put it all back together

Checked the timing and points (not really sure what i'm doing but they seemed in good condition and gaps were ok)

Cleaned the exhaust baffle, a tonne of crap came out of it so i assumed this was the problem.

When i ran it before cleaning the exhaust, it was still forked, complete loss of power at the top, could only go about 20mph, after cleaning the exhaust, the engine ran sweetly for about 10 -15 mins until it was warm, then slowly started to lose power until i couldn't get over about 40mph.
When i stopped i noticed a fair bit of oil on the front side of the engine and exhaust, seeming again to be coming from the spark plug. I changed the plug but it made no difference.

Anyone got any idea at all?
I'm thinking it could possibly be a cracked head or fuel supply problem, possibly even a larger lump of coke in the front of the eaxhaust, is it worth taking the whole baffle off and soaking it in caustic soda or something?

Wish i'd bought a 4-stroke

Post by **Tumble** » Tue May 15, 2007 12:24 pm

It's not something daft like the choke's stuck on is it? If it is, it'll be over fuelling and drowning. I had the same issue with my first bike. Just needed a blast about without the choke for ten minutes and it was fine. Might need to clean the plug again though...

Post by **Dangerous Bob** » Tue May 15, 2007 9:50 pm

It could just be that she's running too rich, hence the heavily carbonised exhaust, but if you're getting oil up from the crankcase, that'll be new piston rings required.
2 stroke though, so check what the fuel/oil mixture's like.
If that's oiling the plug up, you'll lose power quicker than Trigs losing hair.

Post by **Hippy** » Wed May 16, 2007 10:19 am

Someone else has suggested the piston ring, i've no idea how to check it though, bottom end rebuild?

The plug is pretty black, but not particularly oily, again, i dont know what a 2 stroke plug should look like, if that plug came from my car i'd think it was running rich.

Re, the choke, it seems to idle well and wont start without the choke, so i can possibly rule that out? i'll have the carb open and have a look though.

The exhaust probably hasn't been cleaned out in years, so i've no idea how long it's been building up in there.

Post by **Tumble** » Wed May 16, 2007 4:25 pm

Mine needed the choke out to start as well, but it was the sort that you clicked on and it stayed where it was. Because the motor was cold it'd run nicely for about 10 minutes then bog horribly and eventually just stop because it was drowning in fuel. PLug shouldn't be oily really - all the crap should burn pretty well, so if it is oiled up and black looking, then it's running rich like you said.

Post by **Hippy** » Wed May 16, 2007 4:41 pm

My choke is a lever type, seems to not have much free movement at the bottom, so could perhaps be sticking, i'll have a look later.

Post by **Screwy** » Wed May 16, 2007 7:17 pm

You checked the air filter ? if thats crudded up you will run rich and by your description of the plug it sounds like you are , Also check you have the right grade plug installed and make your the oil pump is adjusted properly , Oh and make sure it's a decent two stroke oil in the tank , the previous owner wouldn't be the first person to chuck motor oil in

A cracked head whilst possible is a bit unlikely , remember theres no valve opening's in the head ,just the spark plug hole so a crack would have to run from the plug hole to the edge of the head .

Just pop the head and barrel of to check the rings , Usually you remove the rings and push them back into the barrel then measure the gap to check for wear . Also check for scored piston and/or barrel

Post by **Hippy** » Wed May 16, 2007 9:55 pm

Not quite with you screwy, pop the barrel?
the bore wasn't scored and no ovalling to the piston or bore either. . .

I'm pretty sure i've found the problem, cheers tumble, it appears as if the choke is stuck half way.
Not sure how to unstick it though, i cant see how it operates without removing the carb.

Also got a lot more crap out of the exhaust, but managed to shear a bolt off while putting it back on.

Post by **Class--** » Wed May 16, 2007 10:09 pm

Hippy wrote: but managed to shear a bolt off while putting it back on.

the singal most anoying thing about old bikes !!!!
dont talk to me about shearing bolts i f in hate them

Class

Post by **Screwy** » Wed May 16, 2007 10:14 pm

Hippy wrote: Not quite with you screwy, pop the barrel?
the bore wasn't scored and no ovalling to the piston or bore either. . .

I'm pretty sure i've found the problem, cheers tumble, it appears as if the choke is stuck half way.
Not sure how to unstick it though, i cant see how it operates without removing the carb.

Also got a lot more crap out of the exhaust, but managed to shear a bolt off while putting it back on.

Pop as in take of the barrel

sticking choke will do it , if your taking the carb off check the emulsion tube for ovality (The hole the needle goes into )

Post by **Hippy** » Wed May 16, 2007 11:57 pm

i know what 'pop' means, what's the barrel? you mean cylinder bore? or the bottom of the engine above the crankcase?
It's all cast as one piece, that's why i ask

Yeah class, when i changed my head on the spit i sheared 3 manifold studs off in one go!

So, i have to take the carb off to reset the choke then?