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LT80 Running Issue

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Old 11-10-2018, 05:37 PM
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Default LT80 Running Issue

Hello
I am new to this site I have a running issue on my lt80 and canít figure it out and think I have tried everything. I am a car mechanic for a living so have mechanical knowledge but feel as I am missing something here. Itís a 2000 lt80 I just purchased it and has been having this bog falls on its face at WOT if you back off the throttle and get back on it then itís good for another 7-10 seconds and will bog again. I have rebuilt the carb and cleaned it 2 times now all new jets and seals/ float. I even bought the factory Suzuki jet seals to make sure there is no sizing issue. I put a 90 main jet in to try and help it got a little better so then I started playing with the needle clip position runs best with clip at top highest spot but still bogs only at WOT. Also I have to block the vent tube on the carb for it to run without bogging at lower throttle as well. So this is all testing with the vent blocked. Every change I tried I also tried with vent open and with it open it will bog at any throttle position but idles good. Also with vent open it smokes a lot more than with it blocked off. I donít see any clogged jets or passages in the carb I can see light through passages. I did not boil the carb do you think that would help? I have a new spark plug in it NGK dealer looked it up number wise. Itís all stock besides the twin air air filter. No blocks in air box that I can see. Oil injector is blocked off. There are no vac leaks I tested with carb cleaner. I cleaned reed cage and flipped reeds they appeared to be good/newer. I run no ethanol fuel with redline mix 32:1 (Runs great in my ds80). New air intake boot. New carb/reed cage insulator. Replaced fuel petcock due to factory one leaking with a replacement one from amazon it only has on and prime no reserve. I run an in-line fuel filter after petcock. Compression is 120psi. Checked exhaust it doesnít seem blocked and no restrictor plate and I do have the bolt out of the muffler. Not sure what Iím missing I think I covered everything. Not sure if petcock is crappy I can see the fuel line has a bubble in it before filter but filter is always full I have also tried running it in the prime position when fuel is always going to the carb and made sure petcock does work properly in this position, either way it still has the bog. Should I check gap on the plug what should it be ? But also still doesnít make sense why I have to run it with vent blocked. Runs pretty good this way until about 7-10 seconds into WOT then it bogs and have to play with the throttle. Will do a wheelie from a stop with vent blocked. Is it possible that the fueling is ok and the spark could be cutting out ? I know itís a 2 stroke and should smoke but seems excessive compared to my ds80. Any help would be much appreciated !
 
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Old 11-11-2018, 02:49 AM
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Float level? Fuel filters can be a bit restrictive of flow, on gravity fed fuel lines too. Also can the exhaust take all the gasses at wide open throttle? Two stroke exhausts do need cleaning out sometimes, especially if it is a smoker.
 
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Old 11-11-2018, 08:03 AM
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After all that, I agree w/merryman. Take the pipe off and burn it out. I put it in a fire and get it red hot, then blow compressed air thru. CAREFUL it'll throw flames!
 
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Old 11-11-2018, 10:02 AM
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Thanks for your advise. Should i try taking the fuel filter off or adjust the float? My float itself is plastic the clip for the needle is metal. Should I buy a new exhaust for it or any other way to clean it out good? I donít have access to a large fire pit to put it into. I noticed when I bought the machine the one exhaust stud was missing causing the exhaust to be loose at the cylinder. Yesterday I bolted it back up properly and it still has the bog. It seems to have good flow out the back of the pipe but I understand that it can still be compromised and not letting enough flow though due to the oil mixture. I take the baffle out of my ds80 every few months and clean it up so I know what they can get like inside. I feel like Iím running out of fuel at WOT. The petcock I got still has the vacuum diaphragm on it for the on position just no reserve. Would the exhaust cause me to have to run the vent port blocked? Could this be crank seals or a bad head gasket ?
 
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Old 11-11-2018, 10:04 AM
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Also should I be safe to run the throttle needle clip at the last highest position? Since this is where it has the least bog?
 
  #6  
Old 11-11-2018, 04:26 PM
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Maybe a crank seal. At this point It's a fair bet. For 5 bucks I'd say go for it. Can't hurt. And you can do clutch maint. and such while apart.
I doubt it's a head gasket. It would run bad all the time if at all for very long.
Nobody you know has a place for a fire eh? Charcoal works too. Gots a grill?
I have no idea (at the moment) on why it runs w/vent plugged.
What you mean "jet seals"?
 
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Old 11-11-2018, 07:27 PM
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The clutches were done before I bought it I was told but I would deff do the maintenance while apart. I have a small fire pit I could try or I have a gas grill? Could I use a torch and heat it up until it glows? I meant jet seal under the main. I read in a post some of the aftermarket kit seals squash and donít let enough gas through the port so I got one from Suzuki. So I played around with it all day and changed a few things and noticed some differences. Put the plug back in that came with it when I bought it looked fine I just changed it to change it. Took the fuel filter off that I had and got a new one that pretty much is a screen on the inside for better flow. Installed a shut off valve close to carb inlet and run the petcock on prime and just use the shut off to turn the flow off. Removed petcock and took plastic screens off. Blocked the vac port for petcock on the carb by reed cage. Checked all my grounds fuses and all connectors to see if they look correct and all looked good. With all that didnít really notice a difference. So I tried playing with the throttle needle and cable adjustment. Found with the needle clip at highest setting with cable adjust all the way down seems to rip with the vent blocked and have better WOT time but still has it there. If I take the vent cap off the carb and run it open itís a dog through out any throttle range. Also tried cable setting all the way down with needle clip at highest setting and took out the plastic washer spacer under the needle and seemed to run pretty good only with vent blocked. With vent open again itís a dog at all throttle ranges and bogs/sputters and excessive smoke out the pipe. Didnít run it long with it set like this not knowing if Iím gonna harm something. Iím lost 🤷🏻Spam word ♂️. The plug I took out is a NGK BP7HS
 
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Old 11-11-2018, 07:44 PM
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If Iím getting down to the crank seals I will definitely Maintenance the clutches. I meant seal the one under the main jet I read in a post that sometimes the aftermarket ones that come with the rebuild kit can squash and block the passage so I got one from Suzuki. I have a small fire pit or a gas grill? Could I use a torch to heat it up until itís glowing red? I played around with it all afternoon. I put the spark plug back in that came with it since it still looked good. I installed a new in-line fuel filter that has a higher flow itís pretty much just a screen inside and install a shut off valve next to the carb fuel inlet. I took the plastic screens off the petcock and blocked the vacuum line near the reed cage. Found running the needle clip at the highest position with the throttle cable adjusted all the way down and vent port on carb blocked and plastic washed under needle removed it rips and seems to have better WOT. With the vent open itís a dog at any throttle range and will bog/sputter and smoke escessivly out the pipe. I did not run it long with this setting since I did not know if I could cause any harm to it like this. The plug I had in was a NGK BP7HS and only had 1 tank of fuel run with it in. Iím lost 🤷🏻Spam word ♂️ I also checked all connectors grounds fuses to make sure everything looked ok and it did.
 
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Old 11-11-2018, 07:52 PM
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Plug I took out that has 1 tank run on it
 
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Old 11-12-2018, 03:01 AM
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Looks like all you can do with float level is check the seat is fitted properly. I would be tempted to try it without the fuel filter just to see if it makes a difference, but I still think it could be exhaust. I am lucky enough to be able to run engines without exhausts to check this, as the workshop is on a farm.
 

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