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starting woes 01 Sep 2019 08:06 #810177

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Hello All: I have mined this excellent site for info during my rebuild of a 1977 KZ650 over the past 4 years. Now I need to ask a specific question. My bike runs well; idles, pulls; responsive. The problem is getting it to start. I doesn't like choke. It turns over, coughs a time or two and if I have enough battery or kicking leg available it will start to link coughs , three at a time, four at a time (you get the idea) until it will start to run and I am able to very gently feather some throttle until it actually starts. It often wears out the battery and my leg before that happens. There is a fair amount of backfiring through the exhaust when it first starts, but there is no cloud of smoke or exhaust. Is it starving for gas?
I put in a clear gas line and can see there is gas reaching the carbs. The carbs have been rebuilt (by me, so there may be room for concerns). The carbs have been balanced twice (to ensure they were right the first time).
What and were do I look now? Appreciate any advice offered!
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starting woes 01 Sep 2019 08:13 #810178

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That's definitely not normal. Every 650 I've worked on would always start easily in one or two kicks, even if the carbs were messed up and didn't run right.

Before you get too far into carbs, have you checked the basics like compression, and ignition?

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starting woes 01 Sep 2019 08:22 #810180

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When was the last time the valves were adjusted?
Steve

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starting woes 01 Sep 2019 09:40 #810184

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the valves were shimmed when the 'real mechanic ' had it.

really appreciate the probing

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starting woes 01 Sep 2019 09:57 #810186

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LoudHVX; My reply may have been lost in the ether. As these are my first posts I'm not sure of the process. My reply was something like: Compression seems good on the road and was in spec when I left it with a 'real motorcycle mechanic' last fall. I have only put 200kms since. I had a friend follow me yesterday to check for smoke under hard acceleration, and it pulled very well and cleanly - better than his. It was a pile of rust that had been in a shed for over 30 years, so it actually only has 32000 kms.
Ignition changes - new points, condensers, plugs, rectifier, coils, ... . Timing set by a professional.

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starting woes 01 Sep 2019 10:18 #810188

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In general the 650s are rather cold blooded to start. You say it does not like choke. These carbs do not have a choke that limits the amount of air, rather they have an enricher system that adds fuel. Have the carbs been cleaned or re-jetted? Are all of the enricher (choke) tubes present in each carb. The early B1s came with pilot screw carbs and have an additional #50 jet that sits below the actual pilot jet. This extra jet acts as a limiter to the amount of fuel that the pilot jet can pull up. Others came with carbs that have an air screw and no additional #50 jet. And a few came with carbs that have both and air screw and a pilot screw. It would help us to help you to know which type of carb you have . I would also check fuel level in the bowls.
1977 KZ650 B1
Pods and Denco header


This is my Z

OLD KAW OWNERS SMILE ALOT

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starting woes 01 Sep 2019 12:47 #810192

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I've owned my 1977 KZ650 since it was new (42years - 62,000 miles). I never have had problems starting it, but I don't pull the choke lever all the way up. I pull it maybe 75-80% up, and I do NOT touch the throttle at all. Touching the throttle will almost guarantee that the bike won't start because it conflicts with the choke. If the bike has been sitting for a week or so I generally use the kick starter since the battery may not be fully up to snuff. A couple kicks at most is all it takes. After the bike has run for a minute or so I can ease the choke lever down to the off position. Once the engine is warmed up do not use the choke at all when starting or riding it.

When your bike is warmed up what is the idle speed? If it's too low (less than 900 rpm) maybe that's the problem, but it should not be above 1100 rpm. Also, do yourself a BIG favor - at the very least learn how to check the points to ensure they are in excellent condition and are gapped and set correctly. If they are not, starting the bike will be a problem. Trusting a mechanic is fine, but if the mechanic did not set the points correctly it will be you, not him, that lives with the problem. Points that are worn or set improperly will make starting the bike difficult even though it may run fine once started.

Also, use a JIS screwdriver on the screws that look like Phillips screws. If you need advice on JIS screwdrivers (they are NOT the same shape as Phillips) just ask, if you cannot buy them they are easy to make using Phillips tips as the starting point. Using Phillips drivers on KZ screws WILL mess up the screw heads. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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starting woes 02 Sep 2019 11:24 #810237

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GD4Now: Thanks for the input. The carbs were rebuilt using full rebuild kits four years ago - but only 250 kms (150 miles) since. I used the 102.5 main jets because that is what was in it. With regard to the various modifications KZs may have, mine was exactly like the diagram on pg 44 of the original shop manual - if that helps. I will pull the carbs again to see if they are still clean (never know for sure), and will take a photo if that will clarify the carb makeup. There is fuel in the float bowls, as I drained them a few times while trying to determine if the bike was too much or too little fuel. Is that how I would check for fuel level? Thanks for your patience. raw

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starting woes 02 Sep 2019 11:50 #810238

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650ed: My first KZ650, a 1978 that I purchased in 1980 and rode for 12 years, 90,000 kms, looked and behaved just like yours, so I know what is possible. As I live on the East coast of Canada, the shoulder seasons for bike riding predictably include below freezing temps and high elevation snow, and it never resisted starting after a couple of kicks. This old girl is a retirement project; not the vintage Moto Gussi or Norton that I envisioned, but the price was right (free) and my familiarity with the model were convincing.
I turned the idle speed to 1200 rpm, because below that it stumbled and stalled. Once it is running for a few minutes it is more trustworthy and I could turn it back to spec, but the next start will be the same stumbling.
I am comfortable inspecting points - my other ride a 1950 John Deere M, also needs loving care of the ignition system. I am also comfortable setting the timing, but as I don't have a timing light I have turned to a mechanic to dial it in for me. I will heed your advice a get a light so I don't need to depend on others to get it right for me.
And thanks for the screw clarification. I have replaced every screw I have encountered in this build (allen heads where possible), and ordered packages of small screws for places like the points. The original owner of the bike seems to have fallen over a lot, and relied on butter knives and rocks for tools. So yes, I will like to have information on JIS drivers.
thanks raw

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starting woes 02 Sep 2019 13:07 #810241

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1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
The following user(s) said Thank You: rwhitney

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starting woes 18 Sep 2019 07:44 #811013

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After a long radio silence, I have news. Prompted by your questions, I took the time to read and understand the excellent section on how these carburetors work in my KZ650 Motorcycle Shop Manual. The logic nickle dropped. The concept of three different systems with four jets means that starting without choke requires turning over the engine until I get compression and heat enough to start without the starter jet. That's what I have been doing! So I pulled the carbs, cleaned the plunger tubes, starter fuel passages, starter pipes, and starter mixture passage. I had not cleaned these before because I didn't realize their importance - I cleaned what I could see and replaced the jets. What a rewarding sound to hear the old girl fire up right away on full choke! Thanks for all the inputs on this forum. Sometimes it's not the answers, but the questions that solve the problem.

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starting woes 18 Sep 2019 07:48 #811014

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Thanks for the information on JIS screws. It explains a lot, including why an old Japanese impact driver I bought in 1980 has bits that fit my motorcycle's screws so well. I use the bits in other holders even when not using the driver handle. raw

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