Lexmoto Venom Carb Query

[waffle38930]

Hello all,

I recently picked up a Lexmoto Venom 125 to use while I pass my test, but after several mechanics have spent time looking at it, the general consensus is the carb is just rubbish. I've tried a direct replacement from online but still displaying the same issues.
My question is, does anyone have this bike and if so, does anyone know of a high quality replacement carb that will bolt straight onto the bike? The carb on it currently is a PZ26, I'm not confident in just taking the plunge on another carb without some help, as my thought process is a decent carb is going to cost me quite a bit more than the PZ26 I got online.

Any help greatly appreciated, Thanks in advanced!

[Easy-X]

What sort of issues do you have?

PZ26 sounds like you have a (knock-off) Keihin carb. Simple, single cable, slide operated. I doubt there's anything wrong with your replacement but is it correctly jetted?
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[lingeringstin...]

You don't really need to spend a lot of money on a replacement carb for that bike. I've found those knockoff "PZ" carbs are actually pretty good and very cheap. I'm currently running a PZ27 on my bike and it goes very well. But my bike's not normal and I had to do weird things to the carb to make it work right but now it's great. I think it cost me like fifteen quid off Aliexpress initially. Fortunately I had a zillion spares and bits so I could mix and match things until I got what I wanted which is a complicated story I won't go into here.

However, there are some things to look out for.

Some of those carb lie about what size they are. For instance I've seen them claiming to be 30's but the bore was exactly the same as the 27.

Also the really crap versions are made of less than monkey metal and that can cause all sorts of problems. I've seen sticky slides and air leaks caused by overtightening the nuts causing the carb to actually distort.

Cheap replacement jets are often unmarked so you can't even tell what size they are.

If the carb you have is a replacement already then chances are that yes it's just a shit carb, but a bog standard 26 or 27 off Aliexpress should do you fine for very little money if your bike's still fairly standard (like it still has an air filter and shit).

[waffle38930]

The bike won't idle when cold and barely idles when warm. Until the engine is really up to temperature, I have no power when wide open, it just bogs down. I tend to be lucky to hit 35 while it warms up. It gets easier the more its run but still will bog down 9/10 when the throttle is turned all the way. Even when running "nicely" the top speed is only about 55, it seems like the bikes just not getting enough juice. I've had 3 mechanics look at it and just state its a terrible carb and to sell it for another bike, which just isn't helpful. I have no idea what I'm doing tinkering with a carb and no one else seems to want to do it, paid or not :') So slightly losing the will to live.
It's my main commuter bike so its getting a little painful, though the bike has always been reliable in the sense, its always gotten me where I need to be, albeit like dog poop.

Thanks for your replies, any further help appreciated.

[Easy-X]

When people say "crap" (as in the overall design of the carb) what would be more accurate is "basic." It's not going to allow the engine maximum performance across the entire rev range but you're commuting, not racing 55mph? Probably lucky to touch 60 even with a perfectly working carb anyway.

Poor idling and a chunk of power missing sounds like a problem with the pilot jet or choke. If I was dicking about with it I might try swapping in the pilot jet from the old carb (and double checking the jet is clean.) I'd also pop the air filter boot off and make sure the choke opens and closes properly.
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[lingeringstin...]

If the carb is fairly bog standard and looks clean then scrutinise the air filter gubbins. A filthy air filter will starve the carb of air when you open it up, and often people remove the air filters altogether thinking it'll make the carb breathe easier but it doesn't work well.

I have nothing for an air filter on my bike but a bit of screen to keep children and small dogs from being sucked into the engine. However, I'm running a PZ24 needle in a PZ27 carb (it's a shorter and pointier needle) which evens out the fuel/air shenanigans really well. Goes like stink. But a bog standard carb will need something close to a bog standard airbox/filter to work right usually.

[ElaineSalguer...]

[Evil Hans]

My daughter's Lexmoto Hunter had similar symptoms, and it turned out to be a poorly seated air-filter - it was letting too much air in.
____________________
Triumph Sprint ST 1050. And it's Red.