SuzukiSavage.com - dies under acceleration

fang

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Re: dies under acceleration
Reply #15 - 02/15/19 at 07:35:55

batman wrote on 02/12/19 at 19:33:09:

OMG! A velocity stack is terrible !!!!!! ( even a cone filter-which isn't great- would be better) it will never work with a main jet as small as the stock 147.5 and the stock 52.5 Idle jet, the bike is running dangerously lean !!!!!! It's no wonder it stalls when the throttle is open! You'll need to get a proper filter , do the spacer mod and go to much larger jets , and I'd hate to ask what you're running for a muffler , (but I hope it's not a straight pipe) you should tell us as that also affects jetting.

The velocity stack has worked for the past few years but I'll let him know the cone filter is a better option
I'm not sure what numbers he was reading me but I now have the carb and i'm looking at the jets, here are the numbers

152.5 on the main jet
55 on the pilot
230 on the main jet in the upper diaphragm
45 on the smaller jet in the upper diaphragm

i cleaned the slide, not much residue on it
i checked the needle in the slide, the plate was put on correctly, i can see how it could block the holes in the bottom if put in incorrectly, the spring was installed correctly and there was one thin washer under the clip on the needle

the float seat was removed and the screen was cleaned, i found a decent sized chip of aluminum in there!
seemed like when the carb was made a small piece was lodged in there, it could have been blocking the fuel flow
I got access to the transient enricher, it was kinda dirty but it's clean now!

I have verified all the ports in the carb are clear and free of debri

When i initially cleaned it i didn't realize the needle jet under the main jet could be removed, it has been cleaned as well

He has open pipes with the exception of a baffle at the end of the pipes

What im thinking could have happened was maybe he put the top jet from the diaphragm in the bowl, they appear to be the same thread size

The enricher was removed and cleaned
Hopefully i can get it back on his bike to test it today

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« Last Edit: 02/15/19 at 08:53:32 by fang »

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batman

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Re: dies under acceleration
Reply #16 - 02/16/19 at 18:52:08

So a velocity stack and a drag pipe with a baffle at the end , Jetting doesn't get much harder. Even if you do a good job ,the bike may only run well at a narrow power band near Wide open throttle. The jets you use will need to be more like 55 pilot -155 /157.5/160 main jet and 2- #4 steel washers for the needle jet (spacer mod).Don't expect mileage to be more than about low 40's.
If the velocity stack has been on the bike 3 years ,I'd be doing a compression test/and /or pressure test, to check piston .rings ,cylinder walls and valve guides . A low reading would indicate wear/damage caused be poor air filtration , as these stacks are meant for racing only, bikes that are rebuilt often, not street bikes which log thousands of miles.

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« Last Edit: 02/17/19 at 20:59:53 by batman »

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fang

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Re: dies under acceleration
Reply #17 - 03/18/19 at 10:05:58

batman wrote on 02/16/19 at 18:52:08:

So a velocity stack and a drag pipe with a baffle at the end , Jetting doesn't get much harder. Even if you do a good job ,the bike may only run well at a narrow power band near Wide open throttle. The jets you use will need to be more like 55 pilot -155 /157.5/160 main jet and 2- #4 steel washers for the needle jet (spacer mod).Don't expect mileage to be more than about low 40's.
If the velocity stack has been on the bike 3 years ,I'd be doing a compression test/and /or pressure test, to check piston .rings ,cylinder walls and valve guides . A low reading would indicate wear/damage caused be poor air filtration , as these stacks are meant for racing only, bikes that are rebuilt often, not street bikes which log thousands of miles.

The velocity stack was supposed to be temporary but getting this guy to buy parts is like pulling teeth
Luckily fate has left him in a situation where I now have full control of the part ordering/installing

The first order of business was getting a pod filter, it's on the way in the mail
I replaced his stock petcock with an aftermarket one from ebay, the pill shaped o ring sealed up just fine and it's now gravity fed, 3 position, on off and reserve
I also installed a small inline fuel filter

I'll be ordering some mandrel bent pieces as well as a small baffle soon to make him a new exhaust

I took off the exhaust pipe and cranked the engine a few times to verify the valves where all moving, looked into the carb inlet and they where all functioning as they should

The problem kept pointing at the carb slide, i verified there was no leak from the top diaphragm cover by lightly blowing into the overflow tube while sealing the other outlet holes with my fingers, it went up like i expected

I started researching jet sizes and stumbled across a picture of the slide needle with the spring under it.......wait.......spring under it.......

I took the top cover off, pulled out the slide and took the needle plate out of the slide body, there it was, the spring, sitting ON TOP of the needle....

I had taken the needle out a few weeks ago and thought nothing of it, i guess my buddy must have put it on top of the needle the first time he cleaned the carbs a few months back

Thinking about it, the needle would have excessive pressure down on to the main jet, which would starve it i assume
Only time will tell, I'll be picking up a few gallons of gas today to try it out and hopefully get him back on the road

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batman Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 3806 osceola new york Gender:	Re: dies under acceleration Reply #18 - 03/18/19 at 23:07:48 The in line filter can cause problems (CAN BECOME AIR BOUND STOPPING FLOW) and is basically unneeded , the fuel is filtered in the tank and above the float bowl valve.
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