Lt80 carb help
#1
01-21-2018, 09:29 AM
Lt80 carb help
i
New to the forum and there appears to be a ton of useful info here! I have scrolled thru a lot of the post and I still have not found an answer to a carb issue so I figured I would ask . I bought a 2005 lt80 with the standard Petcock issue I did replace it with a regular petcock the bike at some point had ethanol fuel in it and the gas cap and old petcock were both rusted. That being said I put a new carb on it new fuel with a yellow filter drain tank and cleaned all before the new carb. The little thing starts and idle fine and takes of great until half throttle and then bogs down.... I can slowly get it up to 3/4 throttle but will not run wide. Open and it is Smokey ( but that is another issue) are there any adjustments on the carb straight out of the box I should be making ? I have tried to run it with the air filter both on and off to see if it was air issue.... is there anything I should be checking to help diagnose the problem ? Thanks in advance for the help!Can I add a pic of the plug ? The picture icon is grayed out ... there does not appear to be running rich the plug seems dry
Last edited by koliver811; 01-21-2018 at 10:14 AM. Reason: Trying to add pic
#2
01-22-2018, 11:50 AM
#3
01-22-2018, 12:10 PM
Does "regular petcock" mean gravity fed vs. vacuum fed? I'm going to assume gravity...
Sounds like it's not getting enough fuel...you can confirm this by running it at that boggy point for a bit then kill the motor...pull the plug and tell me what you see. If whitish it's running lean...if blackish way too rich.
If plug is dry then I'd say fuel starvation...validating this is a bit trickier. First I'd disconnect the fuel line from the carb...turn the petcock on...should be a good steady stream of fuel...if not then you have a venting or petcock issue.
If you see a steady stream, then you need to confirm that fuel is getting into the carb bowl and that the float isn't sticking. Re-attach the fuel line to the carb, remove the carb enough so you can take off the bowl cover...turn on the petcock...you should see a steady flow coming through the carb...now manually operate the float and ensure it's not getting stuck in the up position (check the bowl cover and ensure it's clean).
If all that checks out it then you'll need to confirm jetting...
IMPORTANT - your bogging may have nothing to do with your carb, but rather your clutching...to test - get the rear wheels off the ground, start it and see if it runs well with no load on the motor...if it runs good with no load then you have a clutch issue and not a carb issue...I point this out as folks have spent countless hours chasing the elusive carb phantom...elusive because it had nothing to do with the carb!!!!
Sounds like it's not getting enough fuel...you can confirm this by running it at that boggy point for a bit then kill the motor...pull the plug and tell me what you see. If whitish it's running lean...if blackish way too rich.
If plug is dry then I'd say fuel starvation...validating this is a bit trickier. First I'd disconnect the fuel line from the carb...turn the petcock on...should be a good steady stream of fuel...if not then you have a venting or petcock issue.
If you see a steady stream, then you need to confirm that fuel is getting into the carb bowl and that the float isn't sticking. Re-attach the fuel line to the carb, remove the carb enough so you can take off the bowl cover...turn on the petcock...you should see a steady flow coming through the carb...now manually operate the float and ensure it's not getting stuck in the up position (check the bowl cover and ensure it's clean).
If all that checks out it then you'll need to confirm jetting...
IMPORTANT - your bogging may have nothing to do with your carb, but rather your clutching...to test - get the rear wheels off the ground, start it and see if it runs well with no load on the motor...if it runs good with no load then you have a clutch issue and not a carb issue...I point this out as folks have spent countless hours chasing the elusive carb phantom...elusive because it had nothing to do with the carb!!!!
#4
01-22-2018, 05:45 PM
Does "regular petcock" mean gravity fed vs. vacuum fed? I'm going to assume gravity...
Sounds like it's not getting enough fuel...you can confirm this by running it at that boggy point for a bit then kill the motor...pull the plug and tell me what you see. If whitish it's running lean...if blackish way too rich.
If plug is dry then I'd say fuel starvation...validating this is a bit trickier. First I'd disconnect the fuel line from the carb...turn the petcock on...should be a good steady stream of fuel...if not then you have a venting or petcock issue.
If you see a steady stream, then you need to confirm that fuel is getting into the carb bowl and that the float isn't sticking. Re-attach the fuel line to the carb, remove the carb enough so you can take off the bowl cover...turn on the petcock...you should see a steady flow coming through the carb...now manually operate the float and ensure it's not getting stuck in the up position (check the bowl cover and ensure it's clean).
If all that checks out it then you'll need to confirm jetting...
IMPORTANT - your bogging may have nothing to do with your carb, but rather your clutching...to test - get the rear wheels off the ground, start it and see if it runs well with no load on the motor...if it runs good with no load then you have a clutch issue and not a carb issue...I point this out as folks have spent countless hours chasing the elusive carb phantom...elusive because it had nothing to do with the carb!!!!
Sounds like it's not getting enough fuel...you can confirm this by running it at that boggy point for a bit then kill the motor...pull the plug and tell me what you see. If whitish it's running lean...if blackish way too rich.
If plug is dry then I'd say fuel starvation...validating this is a bit trickier. First I'd disconnect the fuel line from the carb...turn the petcock on...should be a good steady stream of fuel...if not then you have a venting or petcock issue.
If you see a steady stream, then you need to confirm that fuel is getting into the carb bowl and that the float isn't sticking. Re-attach the fuel line to the carb, remove the carb enough so you can take off the bowl cover...turn on the petcock...you should see a steady flow coming through the carb...now manually operate the float and ensure it's not getting stuck in the up position (check the bowl cover and ensure it's clean).
If all that checks out it then you'll need to confirm jetting...
IMPORTANT - your bogging may have nothing to do with your carb, but rather your clutching...to test - get the rear wheels off the ground, start it and see if it runs well with no load on the motor...if it runs good with no load then you have a clutch issue and not a carb issue...I point this out as folks have spent countless hours chasing the elusive carb phantom...elusive because it had nothing to do with the carb!!!!
Thanks for the help I will run it up in the air with no load ... I pulled the plug it looks like it is running a little lean and I ran a fuel line straight off the petcock with out a fuel filter and it still bogged down . I do have a good stream of fuel coming out of the petcock and yes it is gravity fed no vacuum and the vacuum is covered on the carb. The carb was cleaned throughly and I even bought a new carb and filter after I cleaned tank . I was thinking of adding some oil straight in the tank to try and make it a little richer because it seems like the “lean bog” I have heard described and I eventually will block off oil injection and run premix. The clutch idea is interesting flat rolloers could cause bogging? I wish it would let me upload pics from my phon.... Thanks again for the help!
#6
01-22-2018, 09:09 PM
#7
01-23-2018, 07:45 AM
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#8
01-23-2018, 11:30 AM
Adding oil to the gas only leans the mixture out...I'm with Jack on the clutching and possible compression issue. You can also for an air leak in the crankcase...if you take the air cleaner out and put your hand over the carb intake and crank the motor you should feel a strong tug (engine pulse)...if it's weak it's pulling enough fuel to run, but not enough to run under load/higher RPMs...just something else to consider...
#9
01-23-2018, 11:38 AM
Adding oil to the gas only leans the mixture out...I'm with Jack on the clutching and possible compression issue. You can also for an air leak in the crankcase...if you take the air cleaner out and put your hand over the carb intake and crank the motor you should feel a strong tug (engine pulse)...if it's weak it's pulling enough fuel to run, but not enough to run under load/higher RPMs...just something else to consider...
Ok thanks I thought leaner was less oil thanks for clearing that up . I put it up on blocks and hit the throttle great response but it did bog down did it again and as soon as it started to bog I shut it off and pulled the plug and it looked dry... and when it started to bog there was also noticeably less smoke in fact almost none . I am going to pull the side cover now can the gasket be reused ? Anything I should be careful not to do when pulling cover ? And any idea why I can’t post a pic yet ? Is there some kind of restriction for new members? Thanks again
#10
01-23-2018, 12:13 PM
