After inspecting the used bike I purchased during the winter I noticed some JB weld keeping some plastic piece together with a hose on the right carb. Wondering if this will effect the performance of my bike. Seems to run fine other than a small, slow leak from the left carb which I'm thinking is a gasket. Take a look at the picture and give me your thoughts/advice. Thanks!!

This forms part of the vacuum system, which if it leaks will affect the fuelling.  Just replace this cap with a new/second hand one to be safe.

Do you know the specific name for this cap or have any info regarding locating this piece for replacement? Further, if the JB weld is doing an alright job keeping the piece together, would it be okay to just leave it the way it is? Thanks!

Andy.

Hi,
COVER ASSEMBLY,DIAPHRAGM,
Suzuki product number: 1350201DC0  This is the whole top cover, you can't buy the plastic cover separately! 
About £80!!!  $100??  brand new. Same price for left or right version   

if its holding ride with it, but if it leaks you'll know about it, bike will mis-fuel!!  I'd replace it when you can, but look around for the best deal, bike being scrapped for parts, 2nd hand carbs etc.

If you're in Europe go to CMSL or motorcyclespareparts.eu  You can use these sites to get any part numbers as they have all the diagrams for most bikes for all models and years.  good source of information
If you're in the States i don't know, check with your local dealer.
My local Suzuki dealer is cheaper on some genuine parts but stupidly overpriced on others compared to the independent parts suppliers as above, and they get the parts direct from Suzuki Europe/Japan.

Thanks so much. How would I know exactly if there was something wrong with that part? Would the bike run and idle normally or would something be different? Would the bike suffer in performance in any way and in which ways? Thanks kindly!

 Just poor throttle response, hesitation and running out of power. The vacuum assists in the raising of the throttle slide, poor vacuum = restrictive slide.

Would the bike have poor throttle response even when revving the engine in neutral? Would it be a slower throttle response in any scenario (e.g. in Neutral, in gear, in the bottom/top of the gear?). Hope to hear back soon. Thanks!

Andy.

vacuum does't just assist moving the slide. It's the only thing that moves the slide. If it was leaking the bike would start and idle but would have low power (at least that carb) under load. It would probably run fine on the center stand and rev etc. The slide moving up is what opens the carb throat to allow air in and also lifts the needle from the main jet allowing more fuel. But this is basically high load probably >50% throttle and over 4-5K rpm before you'd notice the slide not coming up. I'm guessing it's not leaking. JB weld is the wrong material to fix such a thing but if it's working then leave it alone. If it is leaking I'd put some RTV over the JB weld to get rid of the leaks, or buy a junk carb and pull the cap off rather than buying a new one.

If that was leaking you'd definitely know it by riding.

Thanks for the info. The bike seems torquey in 1st through 3rd, but I noticed in higher gears when I am at mid RPM range (5-7k) and I hit the throttle it's seems sluggish to speed up, unless I should be shifting in a higher RPM range on this bike. I'm a new rider so not too sure about these things, and still learning to shift correctly. I've actually only ridden the bike home once from getting a safety inspection. Right now the carbs are off and I'm going to replace some gaskets later today and hopefully take it out for a ride. Anything you suggest checking for in relation to the vacuum port or any potential air leakage? Thanks for much for your help!

Andrew.

You could easily test this by getting a (preferably clean) piece of hose and see if you can suck anything through it.