Only starts when primed

Need some help - Carbs are my Achilles heel.
Got an 82 650 CSR with Keihin CV carbs. (Don't ask me what size, supplying THIS info took research!)
The bike was in parts for 4 years, just got it back together and running. Its always been hard to start but I just discovered that if I prime it, it fires right up! When its warm, it starts with no problem.
I looked through the past posts and didn’t really see anything close to this, but I did find some info here;
www.gadgetjq.com/keihin_carb.htm
Do I need to clean disassemble and clean out the choke… or…? I’m out of my element on this one so any offerings are appreciated.

I dont have a prime on mine but if memory serves, the prime is used to bypass the vacum petcock and starting it on prime is the right way to start the bike

Same Problem with my 1982 J. Unless the tap is in prime its very hard to start for the first time. I suspect the fuel evaporates out of the carb bowls leaving them dry. On position on vacuum tap only works once engine is canking over so you use prime to start, then move to "ON"

I wish it were that easy. To start it I'm not switching the petcock to prime, but shooting gas into a couple carbs.
One important thing I didn't mention is the bike has no air box, but 4 pods. Don't know if that matters or not.

From what I have been told by a few bike shops, when you put pod filters on, your going to have to most likly resync and tune your carbs. your getting more air now since they are outside the box. your airbox is designed to allow the right ammount of air in. They also told me the best thing to do would be to just put a drop in airfilter from K&N. So I did and It runs great. They mentioned that they have seen some pod filters throw the carbs out of sync so bad that they needed to be rejetted. So if you want to run pod filters you shouldn't have a problem if you have your carbs tuned and synced. But thats my own 2 cents. You might be having a different problem all together. But atlease I hope that what I have learned might help you in some way. good luck.

Post edited by: badboie, at: 2007/06/17 04:05

also when you say prime are you talking about the choke? because if you are then , yes, your bike and most all bikes with a carb need to have the choke open when first starting up. this helps the bike warm up and once your bike's idle evens out then you set your idle so it runs smooth.

Odd, the KZ650 never came with CV34 Keihin carbs... they came with BS32 Mikuni.

Hey CSRchopper,

Does your petcock have a prime position? If so BSKZ650 and Kiwiz are giving you good advice about starting.

If you're concerned about the pods, have you examined your plugs to see if you're running too lean or too rich?

KZCSI

Yes- I have a petcock with - on, prime and res -positions. I've tried stating it with every combination of choke on/off Reserve/on....etc.
I put the pods on because after modifying the frame the stock air box wouldn't fit(ugh) so I'm kind of stuck here. I went up one main jet size when the pods were installed but was puffing black smoke so I went back down one size.
Just replaced the plugs but the old ones looked suprisingly good. Nice light brownish color.
Sounds like the issue may be the wrong carbs all together.(!)
I might have toa make a trip to ebay (via this site of course ) to pick up a set of carbs.

I have an old Z500, and it also has a petcock with "ON", "PRI" and "RES", When its running, its on the "ON" and if you run low on petrol its on reserve "RES". When I first start it when cold, I always switch the petcock to "PRI" (and with the choke on), which bypasses the diaphragm, putting fuel into the carbs. Essentially, the same thing when you put fuel direct into the carbs. I think its because when you leave it on overnight some petrol in the carbs evaporate. Have you checked if your petcock is working properly? The fuel should flow out as soon as you turn the petcock to "PRI" Putting in on prime position will allow more fuel into the carbs and leaving the choke on will ensure a fuel rich mixture making it easier to start. Its not unusual to switch the petcock to prime to start when cold. At least thats my experience.

I'm not sure but isn't that what the prime is for? To prime the carbs before it starts to engauge the vacuum in the "on" position when the bike is running?

Yes, that's exactly how I understand it , and how I try to start. In prime, full choke.
I think I'll try to clean teh carbs up again and see where that gets me.