suzuki backfires loud past half throttle

[pickup-truckin]

One of my trikes, an ALT 125, won't go past half throttle either loaded or in neutral

I can't really tell if the choke helps it, but if I feather the throttle I can ride it around.
Also, if I block the exhaust it runs better and I can rev it up nicely.

The backfiring and bogging was making me think it's rich, but the blocking exhaust part makes me think its lean

Should I be looking into the carb? Or should I be looking at something more mechanical?

[dmfaulks85]

Sounds like it's too lean

[ps2fixer]

I 2nd the lean condition, I'd check the needle jet on the slider in the carb, if it is the factory location and not damaged (ie suck in the carb body), then taking the float bowl off and cleaning it would be the next step. Worst case, it has the wrong jets in it and you have to just revert it back to factory (or adjust to aftermarket parts such as exhaust or adjustments on the intake side like no airbox lid).

If it was running so rich that it would bog at half+ throttle, I'd say the exhaust would be puffing out some black smoke. A plug check will tell 100% lean (white) vs rich (black) or just right (light brown).

[pickup-truckin]

After playing with it more this past wind, I'm thinking its super rich actually. I can smell it in the exhaust. If I feather it the RPMs rise nicely but then it sounds like a choke condition past it. I fully cleaned the carb and put the needle down to the leanest (number 1?) And it runs better but there's belarely enough pep to call acceptable. I thought the Suzy's were supposed to be pretty quick. I might just get a whole new carburetor in from eBay or somewhere. Something muhtve been worn past its tolerances.

[SSLS1]

Possibly check your wiring connections. I was chasing a similar condition that was backfiring under 1/2 throttle or more due to a rich main jet. Once jetting was dialed in and running great (smaller main jetting) soon I had the same problem only worse in that it would not accept 1/4 or more throttle and blue flames were shooting out the muffler with heavy backfiring until the throttle was returned to idle. I knew it was not instantly rich since since the main jet change so I inspected my wiring and found the CDI to coil wire was nearly broke in half. This caused a weak spark that was ok with no load but would "blow out" under a heaver load over 1/4 throttle. It would start, idle and free rev fine but studdered under driving load way worse that when it was just jetted too rich. So check your coil wires, connections and grounding, it might help.

[ps2fixer]

Another thing to point out is timing can cause issues too. Not sure how they are on the Suzuki's though. On a Honda there is 2 screws you pull off the side cover, one to be able to roll the engine over, and the other to see the timing mark. Depending on the model there were different ways to check if the cam is in the right spot.

[jacobfour]

Another thing to point out is timing can cause issues too. Not sure how they are on the Suzuki's though. On a Honda there is 2 screws you pull off the side cover, one to be able to roll the engine over, and the other to see the timing mark. Depending on the model there were different ways to check if the cam is in the right spot.

Make sure have proper spark plug gap as well.

[pickup-truckin]

Ordered parts for it and we'll see where that goes. Appreciate the help. I'll check the wring and the gap tomorrow morn. I hope its something simple..its in perfect condition otherwise.

Update* is it weird that it seems to run fine if I hit a bump/pothole or shift it just right? Then it seems to go back to being blah.

[pickup-truckin]

Carb rebuild kit came..,had a hell of a wknd n got the DRS impounded...the next morning my positive battery terminal was smoking on the truck, and the ALT is still barely running past an idle.

Got a breakthrough tho..I noticed that the lights stopped working. Played with the wiring behind the headlight and it started running great. Racing up to the top of the band. Turn the lights off and then back on...back to square one. Got pissed and threw the screwdriver on the ground. It bounced up into the "gas tank" area (since the actual gas tank is under the seat) and whacked the CDI box. EUR-FKIN-REKA. It runs wonderful. Wiggled it n flick it....lost the RPMs

At least I know what the gremlin was. Now onto the other problems life threw at me. People are getting pretty pennies for a CDI box huh..?

[pickup-truckin]

Thought I had it


I've gotten a carb rebuild, CDI, spark plug, coil, adjusted the valves, and drained and cleaned the gas tank. I've checked over the wiring, and now I can't even hit a bump tight to get it to go


It starts and idles fine, small revs are fine, exhaust smells very rich, the spark plug has been blackish, and no change with lights on or off.
Seems to run somewhat better when its warm as opposed to when its cold and first started. Choke doesn't make a difference either. Choke is noticeable when its idling, but doesn't help it run better when revving it


Id like to get a video up if that would help...



I do a lot of thinking when I'm in the shower. how could I check for spark while the engine is still running? How would I know if the stator is bad? Even though it has a fuel pump, could the primer be creating a vacuum when I open the throttle? ( I came across a thread where someone said they took the primer balls out n it ran fine)

[danbur55]

My 85 lt230g would pop sputter and bang any time you ha e it throttle finally tore into harness Found a ground wire at a soldered junction was loose don't know about the alt but might take a look inside harness for loose soldered joints. Good luck

[pickup-truckin]

Found a ground wire at a soldered junction was loose. Good luck

Thanks. Do you remember where your loose connection was? Might dig into the wires over the next few days
Appreciate the help

[danbur55]

as i remember mine was on left side around the seat front

[jacobfour]

I second the proper spark gap. big spark plug gap can cause back firing.

[pickup-truckin]

okay, so I had a chance to go through pretty much everything. Carburetor is infusing fuel. I put a test light on the wiring and it seems good. I put a timing light on the spark plug wire and it would randomly cut out. consistent with the dying after a certain throttle input. I measured the voltage coming off the engine going to the lighting system, and it goes up to about 20 22 v AC. If I pull that wire...let it arc a couple times, and then connect it and turn on the lights, it runs fine. I don't have a regulator I believe my CDI is that. I have 2 CDIs and it does it on both. The wire that gives the voltage I'm reading is the wire that comes right from the flywheel. At that connection it goes to the light switch and then back to the bucket to light the lights. I'm in the garage now trying to get some consistency to the situation. I'll edit this as I find it


Seems like a switch is turned on when the engine gets warm enough. Ran it for an hour around the trails and if I shut it off for several minutes, start it up, and punch it..it wants to die...until it gets back up to a certain temp. Then it seem like it wants to run, but acts very rich. Spark plug shows rich too but haven't looked at it after it's ran "well" for a while



I've been reading around about ATVs that don't like to rev up, and a few posts have said can issues, namely the exhaust lobe. Before I go tearing this thing down, could that be it?

Could a clogged main AIR jet be any culprit to this?


Most spark plugs are .6 - .8. I have a gap of .72. I understand more low end power is from a closer gap and a more broad upper power band is from a wider gap, so I have it set in the middle