carb help

[octopuskilla]

new guy here with carb troubles. So, bought a bike last year, it is a 1973 tx650, bike ran good but 5th gear would git some sputtering. Took the bike in to have the carbs tuned and $300 later still same issue. Then took it to another bike shop, another $300, which had it for two weeks and they ended up putting the wrong jets into the bike but I didn't find this out until this year. These guys had also damaged one of the diaphrams and tried fixing it with silicone(kokesh motors, supposedly well known in mn). After reading the carb guide I have figured out that the carbs that are on the bike are from the 38mm 76-77 vintage which use the 122.5 main, 25 pilot, with the z-8 (at clip setting 3) long needles, which what was in the bike when I got it. The bike has pod filters with straight pipes(1 3/4-2) cut at angles.

The bike has the following problems:
Idles fine in neutral but I have to slowly release the clutch because the bike will die. The first part of 2nd to 5th gear seems fine but as I git passed 4000 rpm's the throttle shoots up and revs high but no more speed is attainable. If I'm in 2nd-5th and roll the throttle back a bit and slowly bring it back up it runs fine until 4000 then it climbs really fast. The idle will also hang at times then I have to open the choke or blip the throttle, fixes it sometimes. The plugs show rich(black) but bike acts as if running lean. I have read the carb guide, tried the troubleshooting techniques but seem to git nowhere but frustrated.
What I have done to fix this:
diaphrams and carb mounts are both new from jbmindusties(really good guy), new brass float bowls set at 25mm as per guide, new carb kit; jets are 122.5, pilot 25, z-8 3rd position. Cleaned carbs with with cleaner and a guitar string then had them dipped in an acid bath. Cam chain has been adjusted to spec, have pamco ignition and used a timing light to set it. The guide, from what I have read says it is running rich and lean, has both characteristics.
Help...

I'm new to xs's and to this site but goddamn, I'm ready to firebomb this set of carbs.

 

[5twins]

With your mods you should rejet. I can't believe you spent $600 at 2 different shops and they didn't tell you that. I wouldn't be giving those 2 places any more of my business, lol.

OK, if you're ABSOLUTELY sure you have '76-'77 carbs, this is where I would start - 27.5 pilots, 132.5 mains, needles dropped one step to slot #2. I have a set of those that I've run on my bike and that's the jetting I arrived at after several weeks of testing. I have pods, minor porting, and Mike's Commando mufflers. With your exhaust, your jetting may need to be slightly different, but this should put you in the ballpark. Oh, and the racing motor at 4K and above might not be the carbs, your clutch may be slipping.

 

[octopuskilla]

Hey man, seriously thanks. I'm gonna give that a try tomorrow. Yeah and after spending that stupid money I decided to do all the work myself from then on. It's definitely more fun, and cheaper.

 

[5twins]

One more thing, if you buy pilots, make sure you get the correct type. Two styles were used in the 650 carbs and from the outside, they look identical but internally they are different. They flow differently and must be used in the bowl type that was made for them. Your carbs need the VM22/210 style .....

 

[octopuskilla]

oh yep, I'll be checking mine shortly. thanks again.

 

[chopper_mrns]

I just rejetted mine, both main and pilot jets two sizes up from stock, and it's amazing how well it runs.
The right jets go a long way..