[ab_714]

I just finished installing a Cylinder Works 256cc Big Bore kit. Timin was spot on as I double and triple checked all timing marks during install and before I put the valve cover back on. Checked all valves and they were good, exhaust was .009 and intake was .005. I also replaced the jets while it was apart, changed main to 175 and pilot to a 45 and placed the needle clip 3rd from the top on a stock needle. That was all I changed and bike is very hard to start. Finally got it to fire with choke and hot start on and holding throttle open. As soon as I let off hot start and throttle it did instantly. Got it to fire again after kicking for ever and using same procedure as before and same result, fires but won't idle and dies instantly when I let off the throttle.
Any help is appreciated as I am getting very frustrated with the bike. All I need is for it to run good for one last race this year. Thanks again.

[JimDirt]

It could be several things , i would confirm your Accelerator Pump is squirting , by looking at the back of the carb and working the throttle (the subframe/airbox will need to be raised so you can see inside the carb) , the AP squirt should just miss the slide , if it does not squirt at all or it hits the slide this will cause issues , you also need to make sure your actually getting fuel in the bowl and to the spark plug , if the plug is dry after starting attempts , then something is clogged or the bowl level is not high enough

The Hot Start adds air to the system , not fuel , so it leans the mixture , the Choke takes away air and allows more fuel to richen the mixture for starting cold , if you have to use both , then something is definitely either clogged (internally) , or your too rich , or you have a electrical issue and the spark is too weak to run the bike

Have you tried lowering , then raising the needle more to see what , if any difference it makes ?? , this will tell you if you have a lean or rich condition , if you lower it and it runs better then the bike is too rich , if you raise it and the bike runs better its too lean , have you checked the seal on the floating slide plate ?? , is the fuel FRESH ??? , if it was sitting for a few months while the bike was torn down , its most likely only good enough to run your lawn mower , these engines will not run on old gas , if its more than a month old , drain the system and refill with FRESH Premium

What is your elevation ?? , and what was your prior jetting ?? , as i have recently learned here , a big bore kit requires a LEANER mixture than it had when it was a standard bore , so its highly likely you are over fueling the engine

Report back with findings

[ab_714]

It could be several things , i would confirm your Accelerator Pump is squirting , by looking at the back of the carb and working the throttle (the subframe/airbox will need to be raised so you can see inside the carb) , the AP squirt should just miss the slide , if it does not squirt at all or it hits the slide this will cause issues , you also need to make sure your actually getting fuel in the bowl and to the spark plug , if the plug is dry after starting attempts , then something is clogged or the bowl level is not high enough

The Hot Start adds air to the system , not fuel , so it leans the mixture , the Choke takes away air and allows more fuel to richen the mixture for starting cold , if you have to use both , then something is definitely either clogged (internally) , or your too rich , or you have a electrical issue and the spark is too weak to run the bike

Have you tried lowering , then raising the needle more to see what , if any difference it makes ?? , this will tell you if you have a lean or rich condition , if you lower it and it runs better then the bike is too rich , if you raise it and the bike runs better its too lean , have you checked the seal on the floating slide plate ?? , is the fuel FRESH ??? , if it was sitting for a few months while the bike was torn down , its most likely only good enough to run your lawn mower , these engines will not run on old gas , if its more than a month old , drain the system and refill with FRESH Premium

What is your elevation ?? , and what was your prior jetting ?? , as i have recently learned here , a big bore kit requires a LEANER mixture than it had when it was a standard bore , so its highly likely you are over fueling the engine

Report back with findings

Thank you for the quick response and info. When I pulled the old plug it was damp but not saturated, I put a new one in while it was apart. The carb is getting fuel, I can open the drain screw and it fills up a small baby food jar. The jets were stock before I replaced them, 172 and 45 if memory serves correct. They are at home in the garage so I can't verify them. If I am flooding the motor, should I adjust the needle clip or is I better to rejet accordingly?
The fuel is the only thing I haven't changed. Gonna feel like an idiot if that was the problem all along. I'll dump me can in the truck after work tonight and drain the tank on the bike as well. Would it be beneficial to run half Race Fuel and half premium with the big bore kit or just stick with straight premium? I have heard of others doing that when adding such a kit.

Once again thank you for your assistance.

I ride in NW Indiana and Southern Michigan, Great Lakes area I believe the elevation is around 1000 ft.

[JimDirt]

I think 172 is a bit big , , i would be thinking more like 165 or so , but i am not a jetting expert , and yes lowering the needle would lean it out a bit , though not the same as smaller jets , since once the slide is up a bit , the needle does not have as much to do with the mixture as it does at the lower part of the throw , but it still affects it some

And you would be surprised how many bikes wont start because of bad/old gas , i run a mixture of Av Gas or Trick 110 with non ethanol Premium , about 1 gallon of the hot stuff with 1 1/2 - 2 gallons of the Premium when i am racing , but when i practice or trail ride i run 1 gallon of the hot stuff to 5 gallons of normal pump Premium , it idles better and starts easier when the octane is up a bit , but you don't need to run race gas all the time unless your at 13.75-1 or more compression

But by you saying your plug was wet , leads me to believe its rich , the plug should not be wet , or dark , it should be slightly tan or slightly dirty looking , but not black/sooty , and not wet with gas , have you pulled the new one to see if its wet right after failed attempts trying to start it ??

How long did the bike sit ??

leardriver is the resident carb/jetting expert around here , hopefully he will chime in and give you more specific guidance , or hopefully its just old gas and the bike will start right up with fresh stuff

[ab_714]

But by you saying your plug was wet , leads me to believe its rich , the plug should not be wet , or dark , it should be slightly tan or slightly dirty looking , but not black/sooty , and not wet with gas , have you pulled the new one to see if its wet right after failed attempts trying to start it ??

How long did the bike sit ??

leardriver is the resident carb/jetting expert around here , hopefully he will chime in and give you more specific guidance , or hopefully its just old gas and the bike will start right up with fresh stuff

Gonna get a couple smaller jets for trial and error. That sounds like the old plug, I'll pull the new one out and clean it and ale sure the gap is correct tomorrow before I try starting it with the new gas. The bike sat for probably around a month while I worked on it. Thanks again.

[JimDirt]

Sitting for a month could be enough to make it hard to , or not start

Make sure when you test that you do only 1 thing at a time , so you know what is doing what , if you try several things at once , you will not know if what your doing is the sole cause , or if its helped or made it worse

So try the gas , if it still wont start then move on to the Jet size , then try to start it , etc , etc .

[ab_714]

Sitting for a month could be enough to make it hard to , or not start

Make sure when you test that you do only 1 thing at a time , so you know what is doing what , if you try several things at once , you will not know if what your doing is the sole cause , or if its helped or made it worse

So try the gas , if it still wont start then move on to the Jet size , then try to start it , etc , etc .

The world is perfect once again!! Switched out the gas and went with a 160 jet, all the shop had at the time, took a few kicks but it fires every time now. Had them order a 165 jet, may put that in or may just keep it as a spare. It is idling a little high now so I gonna mess with that tomorrow. Thank you again for your help!

[JimDirt]

No problem glad you got it sorted out !!