Chugging when at 1/2 throttle - Ex-500.com - The home of the Kawasaki EX500 / Ninja 500R
 
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post #1 of 12 (permalink) Old 4-8-2014, 1:17 AM Thread Starter
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Chugging when at 1/2 throttle

Hi. 1992 EX-500 is the bike.

I really know GS500's but am new to the EX500 so please bear with me. I can relate to the GS since they are similar. So I have a problem and would like to know where to look when we remove the carbs. I'm in West Seattle if anyone near would like a place to wrench and offer some advice.

Bike was dropped and had a Muzzy exhaust. Do do not know how it ran at 65+ mph or WOT before it was replaced with a new Motad exhaust. I rode it, but no highway rides until after the swap. Motad is a 2:1 and probably is close to stock for performance.

On I-5 at65 mph it is OK. When trying to go faster, throttle over 2/3 it starts to chug like it is flooding or something else. You can SLOWLY accelerate to a higher speed, riding that find line of the throttle between running and chugging.

So doing a test at 30mph, doing wide open throttle she chugs. She goes smooth until you get past the 2/3 throttle. I tried this for a fast acceleration and that 2/3 range seems to always happen.

The bike has had recent maintenance by a shop after I bought it.Gas good. Air filter new. Exhaust new. Plugs new.

I do not know what jets are in the carbs. What should I look for and if jets, go bigger or smaller for the mains? Or would I be better using my time by having ducatiman clean and rejet them?

UPDATE: I just went for a 20 mile (sort of) high speed ride on I-5. It really seems to be 1/2 throttle. Go along at 65-70 and open the throttle and she will chug with that loss of power. Roll the throttle back and at about 1/2 you feel the full power kick back in.
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post #2 of 12 (permalink) Old 4-8-2014, 1:59 AM
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Re: Chugging when at 2/3 throttle

Quote:
Originally Posted by adidasguy
Hi. 1992 EX-500 is the bike.

I really know GS500's but am new to the EX500 so please bear with me. I can relate to the GS since they are similar. So I have a problem and would like to know where to look when we remove the carbs. I'm in West Seattle if anyone near would like a place to wrench and offer some advice.

Bike was dropped and had a Muzzy exhaust. Do do not know how it ran at 65+ mph or WOT before it was replaced with a new Motad exhaust. I rode it, but no highway rides until after the swap. Motad is a 2:1 and probably is close to stock for performance.

On I-5 at65 mph it is OK. When trying to go faster, throttle over 2/3 it starts to chug like it is flooding or something else. You can SLOWLY accelerate to a higher speed, riding that find line of the throttle between running and chugging.

So doing a test at 30mph, doing wide open throttle she chugs. She goes smooth until you get past the 2/3 throttle. I tried this for a fast acceleration and that 2/3 range seems to always happen.

The bike has had recent maintenance by a shop after I bought it.Gas good. Air filter new. Exhaust new. Plugs new.

I do not know what jets are in the carbs. What should I look for and if jets, go bigger or smaller for the mains? Or would I be better using my time by having ducatiman clean and rejet them?

UPDATE: I just went for a 20 mile (sort of) high speed ride on I-5. It really seems to be 1/2 throttle. Go along at 65-70 and open the throttle and she will chug with that loss of power. Roll the throttle back and at about 1/2 you feel the full power kick back in.
Stock Jets are all anyone here recommends regardless of exhaust. As for Ducatiman, I haven't seen my carbs, or re-installed them yet (still waiting on Brown...) but if the laundry list of things he found and corrected is any indication, I suspect I'm going to be glad I sent them his way.


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post #3 of 12 (permalink) Old 4-8-2014, 7:59 AM
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Re: Chugging when at 2/3 throttle

^ your carbs leaving for the trip home today


adidasguy- your chugging at 2/3 not necessarily carbs, many possibilities, but send me your carbs and I can assure you they will be eliminated from the equation


“Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba....” quote Hunter S Thompson

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post #4 of 12 (permalink) Old 4-8-2014, 2:29 PM Thread Starter
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Re: Chugging when at 1/2 throttle

Many things have been ruled out

Not slipping clutch
Not RPM related at all
Not speed related
Gas is fresh
Air filter clean and new
Plugs new

Only other bit of information is when 40* or colder, she gets fussy to start. Choke is sensitive and giving throttle when really cold she likes to die. That almost seems like running lean and too much air kills her. She has to warm up for a minute before you start playing with the throttle.

However, now that it is warm (50* and above) she starts pretty good without choke and takes right off.

Up to 1/2 throttle she runs great and has tons of power. There really does seem to be that fine line at 1/2 throttle where power suddenly goes away. I've gone a distance with the throttle in the bad zone then slowly rolled back and you can feel that spot where power suddenly comes back.

The bike is a 1992. Sat for maybe 6 years after a PO dropped here and quit riding. Supposedly the shop cleaned the carbs, and if they did probably not a thorough job. She has been ridden every couple weeks since I got her about 9 months ago.

Probably best to pull the carbs and let the experts fix them up. Also I have no idea if the PO did anything to them when he put on a Muzzy exhaust.

....and I see the WIKI says all gas tanks are interchangeable? I wanted a near perfect one in black with red, so I'll start looking.

and here is what she looks like today. Still have to fix the front fairing and maybe add a red stripe to the tank or replace the tank. all tail plastics have been replaced. Motad exhaust. Engine bars and rear carrier (Renntec) Many other parts were replaced with NOS or at least newer parts.
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post #5 of 12 (permalink) Old 4-8-2014, 6:53 PM
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Re: Chugging when at 1/2 throttle

Quote:
Supposedly the shop cleaned the carbs
Are you reluctant to ask if they saw OEM parts or a jet kit installed? Seems like they would know.
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post #6 of 12 (permalink) Old 4-8-2014, 7:54 PM Thread Starter
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Re: Chugging when at 1/2 throttle

Quote:
Originally Posted by trhouse
Quote:
Supposedly the shop cleaned the carbs
Are you reluctant to ask if they saw OEM parts or a jet kit installed? Seems like they would know.
Did that. They don't remember and was not noted. Actually, that wasn't asked when they did the carbs or even thought of asking. We will have to determine that by removing and opening them up. I can only guess there was something done when the PO put on a Muzzy.

Being my first time in the Kawa carbs is why I'm wondering what to look for. (I know the GS500 almost from memory having even built 3 from spare parts.)

So is there anything that would cause power loss at 1/2 throttle? Certain passages? main jet issues? Float height? Maybe just an issue with one carb cutting out?

I do have a new tank petcock coming and will put on all new fuel lines. Could it be a fuel delivery issue due to clogged lines?
It isn't tank venting as I did run once with the gas cap unlocked. But that would make the symptoms vary depending on how full the tank is.
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post #7 of 12 (permalink) Old 4-8-2014, 8:21 PM
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Re: Chugging when at 1/2 throttle

You have more than enough experience to figure this out. Why are you replacing the petcock? I would start there. It is very easy to test without removing it from the bike. Pull the vacuum hose and the fuel line from the petcock. Attach a rubber hose to the petcock vacuum port and suck on it while you catch any fuel with a paper cup. You should get a good stream. If a previous owner added a fuel filter, check the flow from the filter. Sometimes the routing of the fuel lines to the filter will kink and cut off the flow. Check the fuel you catch in the cup for any debris.

Next use a small clear hose and attach to the carburetor bowl drain as shown below to check the fuel level in the bowls. The spec is 0.5 mm +/-1 mm above the edge of the carburetor. One bike I worked on had the float level only 5 mm too high. I could hardly make it a mile with clean plugs before the engine drowned in fuel and the plugs were fouled a wet black.
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post #8 of 12 (permalink) Old 4-9-2014, 12:08 AM Thread Starter
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Re: Chugging when at 1/2 throttle

The tank petcock is crappy, leaks and all around junky. So I prefer often to replace with new rather than rebuild an old part. At the same time I will replace the fuel lines with new MotionPro lines (We use that on all our GS500's) and rinse out the tank.

Once tank is off I can check the plugs' condition for lean/rich. Also check the float levels. I have a Morgan Carbtune so I'll also do a carb sync, just in case it is off. Will also check the float levels.

Yes I do have experience, but given how specific the problem is at 1/2 throttle, I was just seeing if people experienced in the EX-500 might have some more specific things that could be the cause of the problem.

One thing I like about the GS500 is easy access to the spark plugs without having to remove anything. The EX is harder to get at them unfortunately. A quick look at the plugs could tell me a lot.
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post #9 of 12 (permalink) Old 4-10-2014, 1:29 AM
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Re: Chugging when at 1/2 throttle

I'm having the exact same issue...I'll let you know if I figure out anything...
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post #10 of 12 (permalink) Old 4-10-2014, 1:38 PM Thread Starter
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Re: Chugging when at 1/2 throttle

When replacement tank and petcock arrive, I'll tear into her.
When is also odd or interesting is that until 1/2 throttle, she runs great. Super power at lower speeds. Only is a problem when trying to go fast up steep hills or if you need to accelerate fast to get pass on the highway or want to go faster than 70 mph. In all normal speed city driving you probably wouldn't notice anything wrong.
Going up over a big hill/viaduct over the shipping canal, I can open the throttle and feel the exact point where power cuts out and comes back in.

I'll post what I find or what I did that made it go away (even if the exact cause wasn't discovered).

Hoping some EX-500 guru has seen this before and can get us close to the cause.
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post #11 of 12 (permalink) Old 5-5-2014, 1:07 AM
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Re: Chugging when at 1/2 throttle

After replacing some main jet needles (the retainer clip wore mine out), and syncing my carbs mine is running fine. I did notice the new needles were a tad longer, so I may have just needed to adjust my old ones....
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post #12 of 12 (permalink) Old 6-8-2014, 12:22 PM
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Re: Chugging when at 1/2 throttle

Im having a similar problem in my 98 ex5-r. At low-mid throttle, until I get above 25/3000 rpm it is sluggish and chugs. After that BANG! And she's off to the races! I had cleaned the carbs, and I might be answering my own question here but im not 100% sure the one spring went back in right.. anyway, new pulgs, filters, fluids all good/new. Ill check the spring when I get the bike out of storage here in a week or so, but like the original poster, Im hoping some guru has had this problem. Sorry for thread jacking... :P
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