over jetted???

shmuckingham · Posted: May 1, 2009, 9:35 pm Post subject: over jetted???

after reading over this site and tx650 service manual- i think that i might be overjetted- i rebuilt the carbs with 147.5 mains and i think #45 pilots. i read somewhere that this is correct but after reading xsjohn talk about cylinder washout multiple times- i am concerned. i have a 2into 1 exhaust. not sure of the diameter- also have emgo cone filters. just got a pamco igntion and 30k black dual output coil. motor is stock otherwise. also have a high idle problem- it will idle for a little bit but it will rev up to 3-4k and stay there. ive heard it could be weak slide springs??? carb boot leak( ive sprayed brake cleaner all around the carbs and couldnt get any raise in idle) i did get white smoke when sprayed directly into carbs?? odd, maybe- please help me out!!

xsjohn · Posted: May 1, 2009, 9:40 pm Post subject: Re: over jetted???

Sounds like atu problems holding it at advance or pilot circuit not clean.....and it can be both...definately not weak slide springs unless a po dicked with them...........xsjohn

jayel · Posted: May 1, 2009, 9:42 pm Post subject: Re: over jetted???

stock jetting for a 73 was 130 mains and 42.5 pilots

shmuckingham · Posted: May 1, 2009, 9:44 pm Post subject: Re: over jetted???

atu- advance timing unit??? i guess i have to just buy new springs for the centrifugal system??? what do you think about my jetting? reasonable?? i know the less restrictive filers will require a bigger jet from lack of vaccum

xsjohn · Posted: May 1, 2009, 9:46 pm Post subject: Re: over jetted???

Think he has BS34's on atu engine....correct me if I read this worng....

Free length of the BS34 slidespring is 4 5/8 inches (laying on its side)......

xsjohn

shmuckingham · Posted: May 1, 2009, 9:48 pm Post subject: Re: over jetted???

xsjohn · Posted: May 1, 2009, 9:52 pm Post subject: Re: over jetted???

Sorry.......thought you had the new carbs......still sounds seroisly overjetted........

shmuckingham · Posted: May 1, 2009, 9:52 pm Post subject: Re: over jetted???

solex with aluminum lids

shmuckingham · Posted: May 1, 2009, 9:55 pm Post subject: Re: over jetted???

damn- when i got it all of the jets were mismatched

xsjohn · Posted: May 1, 2009, 9:57 pm Post subject: Re: over jetted???

read the small numbers on the needle....the one in the slide........to verify year.......

If yours are a 73 carbs it should read 4JN19 and the 4 in the chart means the c-clip should be in the 4th clip position from the top

xsjohn

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

shmuckingham · Posted: May 2, 2009, 10:00 am Post subject: Re: over jetted???

wish i knew why these filters suck so bad- im going to hold the weights in place (fullretard) start the bike- so if the idle climbs- i should look into the pilot circuit? im not clear on how to adjust the screws on the sides of the carbs- it says in the manual to unplug opposite cylinder- turn it out 1/4 turn at a time untill a smooth tickover is achieved. is this correct??

shmuckingham · Posted: May 2, 2009, 10:12 am Post subject: Re: over jetted???

btw- when i changed the jets i rebuilt the carbs- new needles and seats- and i still get fuel leaking out of a bowl. also used some rtv to block off the the passage below the diaphragm for the choke- i was getting a leak and the slide was falling pretty quickly when i blocked of the port on the air filter side- they supposed to fall very slowly. i dont use the choke- should i be okay to run it like this? i could not find the leak- it was in the choke pull mechanism but everything looked good- maybe ill tear it apart and use some syl-glyde (rubber friendly silicon lube/protectant/conditioner) i think it may have been an o ring but im not sure

Retiredgentleman · Posted: May 2, 2009, 11:31 am Post subject: Re: over jetted???

www.amckayltd.com/carbguide.pdf

shmuckingham · Posted: May 6, 2009, 9:31 am Post subject: Re: over jetted???

high idle fixed- cut and bent original springs (advance springs fatigued and swinging open gradually) still have the studder around 4k

shmuckingham · Posted: May 6, 2009, 7:39 pm Post subject: Re: over jetted???

ok put #130 mains back in (they look drilled out- maybe a hair smaller than the 145's i have- but the oriface is longer- does that play a role in the jet size or is it just the diameter?dont mean to be confusing) and 42.5 pilots. (i had 145 mains and 47.5 pilots) runs and idles now- havent checked the studder- i did have a faulty plug though(champion) i switched to ngk bp8e?'s need to figure out the proper way to set idle/throttle stops/low speed mix. the manual is kind of confusing- is it bad to run a dual output coil with a plug lead disconnected?

xsjohn · Posted: May 6, 2009, 7:45 pm Post subject: Re: over jetted???

8's are to cold for all that heavy fuel you are trying to dump on that thing......

The problem with hoging out jets is........you won't really know what you have when you get it the way you want it....... Laughing

xsleo · Posted: May 7, 2009, 4:55 am Post subject: Re: over jetted???

Unplugging one plug wire on a dual output coil can short out the coil.
If you want to use the dead cylinder sync method, when you want to kill one side, hook the unplugged wire to a second plug and ground it to the engine. Make the adjustment then do the same for the other side.
Getting new jets are not to costly and you will know what you have.

shmuckingham · Posted: May 7, 2009, 11:57 am Post subject: Re: over jetted???

i guess i should switch to ngk bp7es? still have that damn studder- it seems like it occurs at a lower rpm with the exhaust on and a higher rpm with it off. sounds like only one cylinder- it clears up after after the revs get so high. maybe ill try and drop the needles?? they are in factory position

gordo · Posted: May 7, 2009, 12:03 pm Post subject: Re: over jetted???

Ham, yea, try that. If it get's better, your going in the rite direction,if it get's worse, go the other way, should get better in the #2 position.That is leaner on the transition from pilot to diaphram slide.

shmuckingham · Posted: May 7, 2009, 5:05 pm Post subject: Re: over jetted???

right now im in the 4th groove out of 5 (2nd from bottom) so your saying try to put them in the 2nd out of 5... ok cool i get it now- i will try that and post back. maybe i should just throw down and get some dellorto pumpers. lol

shmuckingham · Posted: May 8, 2009, 4:06 pm Post subject: Re: over jetted???

moved it to 2nd slot- runs a better but feels like a loss of power

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

deleted

TwistedLeather · Posted: June 10, 2009, 11:19 am Post subject: Re: over jetted???

One thing I haven't seen mentioned is the carb syc. If your carbs are not syncronized the motor will idle quite erratically. I've had instances where the bike would idle fine, but once you revved it once, it would wind up then slowly return to idle...this is a case of badly sincronized carbs...an easy fix. I normally bench sync my carbs before ever installing them by using the tail end of a very small drill bit and screwing in the idle screw until it will fit under one butterfly, then I adjust the sincronizing screw to make the other butterfly gap match. It's a good starting point before actual guage syncronization. P.S....make sure you turn the idle screw back to close to it's original position before trying to start the bike

What Happened to 650rider.com?

Yamaha xs650