hanging revs? too lean?

HawaiianBassHed

HawaiianBassHed

Member
Feb 28, 2010
870
5
54
Kailua-Kona, HI
its for the kids LT80 but I figure 2 strokes are 2 strokes... with my old 4 stroke pitbike I adjusted the air screw and the hanging rev got better and the bike seemed to run cooler. this mikuni 26 roundslide doesn't have an air screw and I was thinking it could be a 2 stroke thing... I just don't want anything to blow/seize the motor I guess... it almost sounds like I have a tapping valve too and was thinking it could be detonation as I know there's no valves LOL.

here's how it started. the bike was seeming off, if u gave it full throttle off the line it sputtered and bogged a little even in the mid rpms to get it to go up high really had to chop the throttle.

so I figure maybe it was lean. I didn't have jets so I played with the needle settings. put it richer same thing. put it leaner and seemed like it helped. put it on the leanest setting and it reved high and smooth. so I decided to get leaner jets, it had a 210 so I got a 200 and 190. I put the 200 in and set the needle to the middle. then started it and seemed like the revs would hang... not sure if it did it with the 210 but I couldn't get consistent revs out of it then so it would be hard to test. I'm gonna try the 210 again tomorrow after work with the needle in the middle again. and also I pulled the head gasket as I read I could do that to raise compression so I may put it back on to test as well. probably do that 1st actually. then change to the 210 if that doesn't work I'm thinking it may help with the tapping if it's detonation... or both could be from running lean which the 210 would cure as well if it's the problem. then set the needle lean again and test again. then try the 200 and start over at the needle except go both ways to see if it needs to run on a rich setting with the 200 jet :) gonna be some long testing. I cleaned the filter but don't have new plugs and figure I probably will hear a difference if things get better lol I'll try to get a pile of plugs too, but I need it to be rideable if I'm going to do plug testing since I need to put it on max load then kill it. probably like a gear'd bike just rev out the lil bike to full speed then stall it....
 
That is strange that the hanging revs go away when you lean it out....it should be the other way around. Maybe the pilot is so off that that's really what's making it happen and the needle position is just hiding that?? That type of thing can happen with overlapping valves such as those in carbs. You can cheat on one to make up for imperfections in the other, but it's never ideal.


On the head gasket thing, I suggest buying a new gasket and torquing it on there properly. You can get thinner head gaskets but not using one is a recipe for a blown motor.
 
I'll get a short vid of it later if I can, I gotta head to work. it hangs only a little but before the rev it idles fine. and I don't recall it doing that before I leaned it.

I think you guys are correct with the overlapping I do understand how the needle and main and pilot all have overlap and control is focused in area's but has a slope to it :D
 
ok, so the motor has hanging revs even with the rich jet set in the middle position... and the tapping is still there too. made a quick vid of the tapping. I didn't torque the head just put it on with a 12v cordless impact about as tight as it was the 1st time. and did it in a X pattern... but I went again today and torqued them by hand about as tight as I could get them with the head gasket on and still tapping... with the rich jet needle in the middle still tapping and slightly hanging revs.

I'll do a plug test on the jets soon and get it closed and try to find a richer pilot jet sometime this week. at this point I'm more concerned with the tapping as I don't remember it doing that before I started messing with it. but it had a pretty mean exhaust leak at the head (no gasket) so I wouldn't of been able to hear it anyway... here's the tapping vid...

LT80tappingnoise.flv video by hawaiianbasshead - Photobucket
 
Last edited by a moderator:
wow that thing makes more racket than a blaster motor does..

wierd sounds just like tapping valves in a 4 stroke... i listened to it twice... little of it sounds like its leaking ether from the pipe flange or the head gasket..... can you see any oil residue round the head gasket or even the base gasket??? if ethe rof them are leaking it will cause the lean hanging like you are having
 
I don't see any, but it could be there... I'm gonna pick up a torque wrench tonight so I can properly torque them tomorrow. I do have a complete engine gasket kit I got off ebay to do the motor for the 94 with and I got a new used crank here as well ready to go on. I actually put a different head on since I had it sitting... I have the head that came off the exact motor sitting... I thought the other one was cleaner so I put it on instead of the one I pulled off...

I don't really need to use a new gasket do I? what's the difference this one is compressed already? I will if I have to, but I kinda wanted to use it on the other motor... I guess I can order another top end set since I used the exhaust gasket already lol

I DID see oil mix in the part where the gasket is supposed to go when I put it on today it wasn't outside of the flange tho, just where the flange is supposed to go... I guess the top I put on could be slightly warped causing the leak... I'll check that tomorrow I suppose... I think I'll have it milled at some point just not sure where to get it done here locally...
 
no, the other motor isn't as far bored as this one. they're stock heads on both off the same type of bike why would it slap the stock head? I didn't pull the piston or rings, just pulled the head gasket to raise compression and put the different head on since it was cleaner. the old one seemed to have pitting in it. so I decided to use this one.. I'll put on the new gasket tomorrow, I don't even own a torque wrench so I need to pick one up. luckily walmart has 1/2" ones for $29 as opposed to the $87+ at home depot and lowes... pita and I did moped heads before and never used a torque wrench, just hand tightened them in a figure 8 as tight as I could within reason. never had tapping before, basically the same as this, 2 stroke big bore, solid aluminum block with fins for a head (I think 2 strokes all are like that?, as opposed to 4 strokes with cams and valves and stuff)
 
It's generally best to always go with a new head gasket when you remove the head. Not that you can't get away with it sometimes....but more often than not, trying to get away with it will burn you.


I would guess that you've warped the head by not having the head properly torqued....especially if it was running minus two bolts on the head!!

You don't necessarily need a torque wrench to properly torque the head bolts. What you need to do, with a new head gasket in there (and after making sure the head is flat, bring it to a machine shop, they can tell you) is finger tighten all the bolts then slowly start tightening them up in a star pattern, just like wheels on a vehicle. Don't crank the first bolt down to fully tight right away! Get it a little snug, and then go to the bolt opposite of it, and work your way around in a star pattern. Don't start tightening them real well until you've got all the bolts somewhat tight from the first go around. You can get a feel for torquing all of the bolts to the same torque. While it wouldn't hurt to borrow a friend's torque wrench for the first few times you do it, after that you can usually do it without a torque wrench....although it's always best, especially with head and cylinder bolts, to get them right at the spec. What I guess I'm trying to say here is that torquing them all evenly is the most important part!
 
that's how I did it, I didn't hit them hard all at once. I gradually went around finger tight 1st.. and snugged them about as tight as I felt I could with the 5" long 1/4 drive socket wrench would let me with one hand...

well, decided to put in the new headgasket and use the torque wrench... busted 2 studs, I think I stripped the block for those same two. busted my thumb up good and just about lit the bike on fire... it's taking alot for me to not destroy it all.... I'm pretty pissed. I don't give a sh!t about the head, it was a spare I can use the good one. I do however care about putting all this time in buying tools for about $100 only to have that entire aspect blow up in my face. if I was strong enough I'd bend the damm tq wrench into a u and throw it in the ocean... Ideally I'd like to find someone I don't like and beat them down with it til I'm content but since that will get me in trouble returning it to the store I got it from is probably a better start...

fukken pissed to say the least. now I'm out a head gasket $100 for the tools I got and the bike is worse off than when I had it before I started... if only I had some dynamite laying around I could go blow some sh!t up... starting with my $30,000 truck :D damm that anger management.... about the only thing that helped was holding my daughter for a little while.. I was pretty much ready to yell at my son to leave me alone I don't think the wife even has any idea how pissed I am. usually when I get this mad she'll pack up the kids and bail or just try to stay away and let me cool off... dunno I'm more disappointed in myself than anything.. if I beat down the motor with the tq wrench tomorrow maybe that'll make me feel better, destroy the top end ruin the bottom with all the little pieces that will fall in, then light it on fire with my propane torch and gas somewhere and just leave it to burn... even that would probably just cause a damm forest fire or something.. just really wanna blow sh!t up more than anything...
 
nah, but he didn't pay for it either LOL

hard to do a swap on these as the motor IS the swingarm so I'd have to fab up a real swingarm and mount the motor inside of it.. make it an under over I thought of ways to do it already and if I did, I'd drop in a motor that's larger like a CR125 motor. other than that it's really not worth it imo I'd be better off starting with a better platform to do something like that...

I ordered a new gasket set so I'll play with it again when that comes in. supposed to be getting a motor case in the mail so when that comes I'll start making it a good engine and throw it in the other LT80 so my kid could ride that... that's the good thing about having a couple bikes... I actually figured I'd ride one with him and get me a regular size bike for myself to ride as if I ride my regular bike with him, I won't really be riding with him... he'd be playing catchup and chase master lol
 
yeah, pita, I'll get it going again. gonna try that red locktite/threadlock stuff on the two partially stripped studs and a new headgasket and torque them a little lighter next time and see if I still get a clackity hanging reving engine LOL... worst case scenario I need to retap the holes and get another head gasket... I'll have a head milled sometime I get off my azz and put it on for fun when I put either of the motors back together... waiting on a motor to come in for LT80#2, so I'll have her up and running sometime in April (I REALLY HOPE) so by then this one should be running well again at which point we can have LT80 drags I guess LOL and see about the swingarm mod. there's a front A-arm extension one of the other members does along with different shocks so the front gets more travel. which you can get the total deal for $160 with your arms sent in to mod which isn't bad :) just gotta figure out the rear swingarm setup and throw on a better shock with more travel and your really talking :D but at this point its probably better to get a Cobra or DDR or something lmao...
 
ended up getting blue threadlock to try and get the studs to stay in place good enough to torque the head/jug down to 10ft/lbs... not sure what else to try other than that... my buddy said helicore from a machine shop would do it and it's like $10? but I don't really want to pull the motor so I'll try this 1st and then if it doesn't work I'll do the helicore...

has anyone ever done it this way? I was thinking I could even use JB weld or something, but then if I want to get it apart I'd have to do something pretty exteme lol... not that I'd need to remove the studs unless they broke again...
 
I was also advised to put new seals and bearings in :( this is turning into a hell of a project... currently haven't removed the clutch or flywheel so I need to pull them before doing the motor... gotta get me a manual I suppose LOL pita, motor was sitting way too long I think stuff is really rusted up... the clutch appears to be functional on the motor I just picked up. the front Variator and fixed face are good as well as the case so I got more than my money's worth out of those parts alone. I also decided I may as well clean it up a little since I didn't get much wrenching work done. so I hit the clutch side cover and motor case a little with a drill buffing wheel and rubbing compound..

this one I'm pointing at what it looked like all over the entire thing. I hit it pretty good with some turtle wax rubbing compound I got from Kmart for like $2... ran thru like 1/4 of it figured I may as well experiment with it :D

DSC04605.jpg


pretty easy to tell the difference in this pic...

DSC04604.jpg


It looks better in person, these I just took and it's 7:30pm so it's dark out and I had to use the flash :( I'll polish it up more sometime and get more pix. figured I have it laying there and am tired of getting my hands coated in crap every time I touched it so I wanted to clean it but the gunk foam stuff is hard to find now adays got the gel and liquid ones which suck :(

polishing them may help the looks of the bike in general I think personally if I get it shiney all over. main thing it gets better looking than stock :D
 
I saw the thread your on at atvriders, the guy on the same thread that goes by "Lt80"
has been working on them for a very long time. I'd take his advice if I were working on one.
 
You must log in or register to reply here.

Similar threads

kyle Nelson
Need advice
Replies
0
Views
349
Engine
kyle Nelson
kyle Nelson
Dragonslayer
Leak down test failed. What now?
Replies
0
Views
307
Engine
Dragonslayer
Dragonslayer
Darey
Bogging down
Replies
1
Views
394
Engine
adces12
adces12
Dragonslayer
Blaster idles, but revs up slowly in neutral and has no power in gear
Replies
1
Views
438
Engine
Dragonslayer
Dragonslayer
Quadrrider2010
96’ Blaster with 240 kit
Replies
0
Views
312
Engine
Quadrrider2010
Quadrrider2010
Top Bottom
Back