Bike dies when taking off choke.

[gottogochop]

you are not making much sense, you say firstly the bike would not start at all, then you cleaned the carbs and synched them.(bench synch?).
then you go on to say it was running before without a problem....when before??

Sorry, So, one day I was riding it and started running like crap (bogging at high speed, headlight flickering), I had to have it on choke just so it wouldn't die. The next day I went to look at it, it wouldn't even crank over, I ended up tracing it back to a bad starter relay. I replaced it, and that fixed the cranking over part. I got it started, for a little bit, I checked to see if the carbs were synched at this point, and the were all fine. the bike sounded bad when it was running. At that point I decided to clean the carbs. after that the bike would start, and run poorly, and only with choke on. I checked the valve clearances and 5 of them were way to tight. so, I re-shimed them this last weekend. I went to start it, after sitting for a month and it was having some trouble getting going so I bump started it (first try too.) It sounded better, but that was only with choke on. taking it off choke kills it, trying to ride it with choke on also makes the motor die.

Is there anyway this could be some weird electrical problem?

[gottogochop]

I totally agree with maddevill, I had the exact same problem that you are having. I pulled the carbs off 3 times and cleaned them and recleaned them and recleaned them, but the problem. After putting in all new jets, diaphrams and o-rings and gaskets, it still did it. i thought they were possessed and I needed an exorcist. Then I carried them up to a local job and had them clean those carbs in their sonic cleaner. When out back on, the bike ran like a champ. The point I'm making is you might think you have cleaned them, but all it takes is a tiny spec of crud to block one of thoser tiny passages. Good luck.

Okay.

What the heck is a sonic cleaner! most shops have them?

[gottogochop]

If the bike runs on the choke and not when choke is off, your pilot circuit is plugged. you have to remove all the pilot jets, make sure they are clear, AND make sure the passages they go into are clear as well. Right now the motor is getting fuel through the choke system, when you shut off the choke, there is no fuel being delivered from the idle circuit. Disassemble and clean and report back.

Mad

Will do...again!

[kdo58]

google

http://www.harborfreight.com/catalogsearch/result?q=sonic+cleaner

[M.A. Jacques129]

Okay.

What the heck is a sonic cleaner! most shops have them?

It's a tub with chimical product and when you start it, ultrasonic is produce and the reaction clean the pieces. Most of the shop have yes, but where i'm working we have another stuff, here we call it 'gunk' and it's very very strong. The aluminium comes bright and all the brass of the carb and jets came bright gold. I cleaned my 2 carb with that stuff and the bike run like new.

[Gorminrider]

what bike is this? I can't tell.
Runs ok on choke? Ignition is ok.gas flow is ok.

CV carbs?
My theory-you pushed the actual jets out? The long ones that the cv slider runs it's pin in? I don't mean the pilot circuit. I don't mean the main jet that you unscrew. It's under that. You must PUSH the main jets out and clean them and all passages that lead to them.

if you haven't got it, from Bass-cliff's site read this.
Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

[BassCliff]

Hi,

Most bikes this age have several problems. Yours has a couple of extra problems because of the modified intake and exhaust.

These items cannot be stressed enough:

Properly cleaned carbs.
Properly adjusted valves.
Clean and properly functioning charging system.

You will find information and "how to" guides on my little website.

You have the additional joy of trying to tune carbs without first establishing a stock baseline. The Dynojet Stage 3 kit will save you a lot of trial and error.

Go through the maintenance lists in the "mega-welcome" and properly address each item. Skipping steps or taking shortcuts will be frustrating at best and hazardous at worst.


Thank you for your indulgence,

BassCliff

[M.A. Jacques129]

5$ on clogged pilot circuit/jet

[koolaid_kid]

Started by completely taking the carb apart, spraying the jets with carb cleaner. took a air compressor to the jets. took the jets out, cleaned them with a tiny wire (manual says so).

This is not cleaning the carbs. You need to either use carb dip or the sonic cleaner, get a set of o-rings from cycleorings.com, and follow the procedure on BassCliff's website. How to rebuild your carbs

[TheCafeKid]

I'll echo the sentiments about cleaning your carbs,
But you have stock jetting and THAT WON'T WORK with that intake and exhaust set up. (Pods and pipes) you're running very lean. If it in fact did run before, I guarantee you it ran like garbage. And through no fault of your own, you don't know the difference because its never run right to begin with.
Running this bike this way will eventually destroy the motor. Mainly the top end.
The burn is too hot, and it will burn the valves.

You need to rejet. I can give you a ballpark on your set up, but you'll still have to tinker with it to dial it in perfectly. I'm assuming your bike is a 77-79 750. Or was before someone had at thee with ye olde hacksaw

Order yourself some 117.5, and 120 main jets. The stock pilot jets will be ok most likely but you may want to order some #17.5 pilots as well.
Get an oring kit from Robert Bar at www.cycleorings.com. You are going to have to completely disassemble the carbs anyway to rejet and move the needle clips so you might as well clean them for realsies.

Post back and we can go from there. If thisis a bit too daunting...PM me and I might be able to help you out further.

[gottogochop]

Okay, I put 105 main jets in, it started with a bump, ran a little bit better. I could take it off choke, but had to really rev it out, or it would die.

I'm going to go way up on the MJ size now. and adjust the needle clip. I also bought an ultra sonic cleaner. which seemed to work well.
The bike is a 78.

[gottogochop]

Hi,

Most bikes this age have several problems. Yours has a couple of extra problems because of the modified intake and exhaust.

These items cannot be stressed enough:

Properly cleaned carbs.
Properly adjusted valves.
Clean and properly functioning charging system.

You will find information and "how to" guides on my little website.

You have the additional joy of trying to tune carbs without first establishing a stock baseline. The Dynojet Stage 3 kit will save you a lot of trial and error.

Go through the maintenance lists in the "mega-welcome" and properly address each item. Skipping steps or taking shortcuts will be frustrating at best and hazardous at worst.


Thank you for your indulgence,

BassCliff

I've narrowed it down to the it being a fuel delivery problem, i'm going to be using the rebuild guide on your website. I just have to find a kit for the VM carbs.

[kdo58]

http://www.cycleorings.com/VMkit.html

kits are a waste of money, you might need float bowl gaskets.

[gottogochop]

http://www.cycleorings.com/VMkit.html
kits are a waste of money, you might need float bowl gaskets.

(I meant "Kit" as in an o-ring kit)

[gottogochop]

Ok, I put a 117 MJ in, it starts without pushing. it was still lean, So I put a 122 in and its a lot better. I just don't understand how one day the bike can decide to quit working with the jets it has. must have been something to do with adjusting the valves. Now I'm only running on 2 cylinders!...must be a bad coil.