Vm34 issue and blow back through the carbs

[Mp219]

Hey there new to the site.

Recently install new vm34 carbs with 57mm kn pods and I custom 2-1 scrambler pipe.

Having issues getting this bike to run right.
Check the valves, made sure the timing was correct.
Getting back fire through the carb and exhaust.
I've pretty much have come to a loss at this point, hopefully someone on here can give me some insight on where I went wrong.

 

[ninskrillz]

Hey there new to the site.

Recently install new vm34 carbs with 57mm kn pods and I custom 2-1 scrambler pipe.

Having issues getting this bike to run right.
Check the valves, made sure the timing was correct.
Getting back fire through the carb and exhaust.
I've pretty much have come to a loss at this point, hopefully someone on here can give me some insight on where I went wrong.

Sounds lean to me! What jetting are you using?

 

[grizld1]

Sounds like insufficient information to me!

Click the Tech section, find the link to the VM section of the Carb Guide, and read it. Also check compression.

 

[kevski]

Sounds like insufficient information to me!

Click the Tech section, find the link to the VM section of the Carb Guide, and read it. Also check compression.

Same here, do you have standard jetting? if so you need to re-jet the carbs to suit the new set up as standard jets with the dreaded pods and open exhaust will have the motor run very lean.

 

[grizld1]

The OP has VM34 aftermarket carburetors.The "standard jetting" on those is what comes out of the Mikuni factory, which is way too RICH for the XS650, even with full race mods.

 

[Mp219]

So your saying come down on the jets?

 

[figure8]

Can you tell us what jets are in the carbs now??

 

[XSLeo]

Did your engine run ok before you installed this set of carbs?
If it ran ok with another set of carbs, then the only issue is with the new carbs.
If you never had it running before it might not be the carbs. What ignition are you using. If points it could be you have the right set of points running the left cylinder.
If the TCI then it could be a weak magnet or low battery voltage.
A bit more info would be helpful.
If you notice a lot of us put the bike info in our signature. This way we can see what the year and model, any mods done and such without having to ask.
Leo

 

[grizld1]

MP, I'm not saying anything except that you didn't get useful advice. You won't get useful advice until you inform yourself and inform anyone who's inclined to try to help you. Hear this, please: THIS AIN'T THE PHSYCHIC HOTLINE.

 

[Mp219]

Sorry I've been around long around all morning. The bike ran when I bought it, only issue was when I bought it didn't charge, bc the guy didn't realize he snap the wire on the front sprocket.

Right now I have a 180 main in it. Came to me with 170 in it. The pilot (correct me if I'm wrong bc I can't really read the writing on them) had a 51, bump it up to a 52.

 

[grizld1]

Oh, that's fine; all there is to tuning is MJ selection, right? Because that is the only piece of hard information you've given: apart from the fact that PJ's that large would foul the plugs immediately if the motor would start at all, 51 and 52 are not Mikuni PJ sizes. If you can't read the numbers, do what you'd already know to do if you'd read the XS650 Garage USA Carb Guide and buy a 10X loupe.

I'm done on this thread. If you want more advice on your carburetors I'm sure plenty of guys who've never tuned a VM carbie will be happy to jump right in.

 

[figure8]

MP, if you haven't yet give this a read.....should answer some questions for you.
http://www.amckayltd.com/vm34-36.pdf

And just out of curiously, you said it came with a 170 and you bumped it to a 180 MJ. Can you better explain the scenario with a little more detail?

 

[figure8]

Damn.....I think I did rub off on him.

Nah, he's on par with himself. And don't sell yourself short, you are your own unique, special snowflake.

 

[grizld1]

I don't intend to sound mean, guys, but it gets tiresome writing the same thing over and over. Part of doing it yourself is a bit of self reliance; I referred Opie to the VM section of the Carb Guide once already. He didn't bother to look and he didn't bother to strip the carbs and compile a jet list. I've put the information out there, it's available, and I won't waste time and effort trying to help somebody who won't bother to do what it takes to be helped.

That's a far cry from looking for opportunities to ridicule the unknowing. I'm patient with beginners who'll try, but when a guy fishes for a quick fix and won't try to help himself, I'm done.

 

[Mp219]

Don't worry show boat I got it. Thanks for your useless help

 

[XSLeo]

In grizld1's first post he said to read the VM carb guide. Did you?
If not then don't bitch at him till you do.
Leo