Suzuki Discussions about Suzuki ATVs.

LT 80 lacking vacuum

  #1  
Old 11-14-2018, 12:02 AM
Trailblazer
Thread Starter
Join Date: Oct 2017
Posts: 41
Default LT 80 lacking vacuum

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
 
  #2  
Old 11-14-2018, 08:22 AM
Extreme Pro Rider
LT80 Expert
Join Date: Mar 2001
Posts: 7,881
Default

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.
 
  #3  
Old 11-14-2018, 08:32 AM
Trailblazer
Thread Starter
Join Date: Oct 2017
Posts: 41
Default

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
 
  #4  
Old 11-14-2018, 08:54 AM
Trailblazer
Thread Starter
Join Date: Oct 2017
Posts: 41
Default

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?
 
  #5  
Old 11-14-2018, 05:41 PM
Extreme Pro Rider
LT80 Expert
Join Date: Mar 2001
Posts: 7,881
Default

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.
 
  #6  
Old 11-14-2018, 09:18 PM
Trailblazer
Thread Starter
Join Date: Oct 2017
Posts: 41
Default

Ya ok. Is there any cylinder and piston I can get as a kit for a reasonable price thatís decent? Just not sure who locally would bore for me.
Also I still am having a hard time accepting without compression test done cause today
I blocked the intake and it started right up and I rode it for an hr.
Had lots of get up and go and it was -5* out !

it will start right back up with starter until it gets fully cold.
Then I need to block intake again.
Still sound like low comp to you?
 
  #7  
Old 11-15-2018, 08:30 AM
Extreme Pro Rider
LT80 Expert
Join Date: Mar 2001
Posts: 7,881
Default

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.
 
  #8  
Old 11-15-2018, 11:12 AM
Trailblazer
Thread Starter
Join Date: Oct 2017
Posts: 41
Default

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
 
  #9  
Old 11-20-2018, 06:55 PM
Trailblazer
Thread Starter
Join Date: Oct 2017
Posts: 41
Default

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
 
  #10  
Old 11-20-2018, 06:56 PM
Trailblazer
Thread Starter
Join Date: Oct 2017
Posts: 41
Default

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
 

Thread Tools
Search this Thread
Quick Reply: LT 80 lacking vacuum


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: