Hey gang,

so I was trying to improve my (and my kids) lt80 ....ha.!

I did brake cables, air filter, new intake boot, straight flo petcock and carb rebuild kit from moose.

It was running ok before but wanted to finish up the job i started. I bought it dead this summer , It was lightly seized because the oil injector had failed.
I disconnected the oil injector put in a new starter and battery, cleaned the carb and lubed the top of the piston it ran. And quite well I thought
( slightly rich I thought) but fine on 32:1 premix. It pulled me and my two kids on it at a good clip and would wheelie with just me on command.
but... I had to mess with it... I am very good at breaking things that are not broke.


anywhoo, a while back I ordered the parts I mentioned erlier for the fixes and installed them all yesterday.

after everything was put back together last night one slight touch of the starter and it purred like a kitten making popcorn.
thats good in my mind . I was super pumped that it all went schmooth.

I let it warm up, drove 10 feet and it bogged.
could not get it started again. tried for 10 min.

Pulled the carb and went to the place I thought was the most suspicious.
that little rubber o ring that came with the carb rebuild kit under the main jet.
it seemed too big and somehow not right. so after the second time i pulled carb last night , I found it restricting the size of the jet, I took it out and put a smaller o ring in its place.
I also noted that the vacuum line wasnt blocked properly so I made a good seal. checked float level with a clear tube also. seems good.
it seemed to me that the gas was not getting into the engine.

a squirt of quickstart and the engine fired right up but only for a sec.

today I learned that if I put my hand over the intake of the carb the bike will fire right up. and stay idling,
I can put the boot back on and go for a ride. So I thought I fixed it by reducing the size of the o ring and tightening up the vacuum port
. Once its warm, I can fire it up no prob. again and again

BUT If I leave it for an hour or two, it wont start unless remove the boot and I cover the intake at the carb.
Its not quite as powerful as before the rebuild but runs well once its started.
mind you its also -2 and snowing

the choke seems to work but its not enough choke to start it . I have to completely restrict airflow to build initial vacuum,
or atleast thats what I have deduced.

could leaky crank seals do this? I would have thought it wouldnt run well with leaky seals ? but it does run well, just wont start well.
should I completely remove the rubber o ring under the main jet? is that making it harder for fuel to get moving untill there is vacuum built from
a running engine? I mean its strong enough to wheelie with me on it so I would assume the compression is ok?

what are your thoughts ?

thanks in advance for taking the time to read this. '
let me know if you have any q's

cheers
Tarik

 

It's a compression issue. Do a compression test to make sure (90 min).
You were lucky to have it run so well after seizing. You need a new bore/piston.

 

Ok Thanks man, I will get a tester and check.
maybe build a leak down tester.
by new bore you mean honing the cylinder?
thanks for your time
cheers
T

 

I guess the whole top end is pretty reasonably priced, was just looking on Ebay,
any brands, or sellers you recommend for a bore and piston kit?

 

They are all the same china junk kits. $13 bucks in bulk.
I recommend getting the next size up Suzuki piston and have the cylinder bored. Any reputable shop can do it. FYI: It'll cost you a lot more than the china kit but it'll last a lot longer IMO.

 

 

Until a gauge proves me wrong, yes I feel it's compression.
Cold= too much distance between piston and cylinder causing a lack of vacuum. Now comes the choke thing and it runs. The motor heats up and expands the piston enough to let it run OK.
That's my version.

 

ok, you make a lot of sense.
comp tester on the way.
will let you know when I get results next week.

thanks for talking this through with me.
I really appreciate it.
cheers
T

 

do you know off hand the size of plugs i need for intake and exhaust to build a leak down tester for the lt80?
thanks
T

 

i read that the exhaust is 28.5 mm , is that inside DI?
and the intake is possibly 21mm? is that inside diameter?
just looking to get some plumbing parts tmr and wont have a chance to measure before hand