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A four cylinder 600cc streetbike engine to lose power when it warms up…

Customer Question
what would cause a four...
what would cause a four cylinder 600cc streetbike engine to lose power when it warms up?
Submitted: 8 years ago.Category: Motorcycle
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Answered in 7 minutes by:
6/29/2010
Motorcycle Mechanic: Kenny O., Motorcycle, ATV, Mules, Side by Side's Product Specialist. All Brands replied 8 years ago
Kenny O.
Kenny O., Motorcycle, ATV, Mules, Side by Side's Product Specialist. All Brands
Category: Motorcycle
Satisfied Customers: 1,022
Experience: Worked for Kawasaki Motors as a Product Support Specialist (Factory Support) for 24 years
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Hi my name is Kenny

 

When you say loose power can you give me a little more detailed info, does it miss, or backfire ? a little deeper info might help me diagnose it.

 

Also if you have the mileage and do you know the last time a major service was performed, that would include a valve adjustment,

 

Also one more thing, how does the bike start when cold ? do you need a lot of choke to start it ? Do you live in California, or do you know if you have a California model ?

 

Thanks

Kenny

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Customer reply replied 8 years ago
ill cruise on the bike and itll run like a champ and starts up just fine i find myself not even having to use the choke but once it warms up it loses power and sounds as if the bike is running on two cylinders but im not sure and it does backfire a little bit but not much it has around 25,000 miles on it i do not know when the last major service was performed and the guy i bought it from said it needs the carbs synchronized but would that be a cause ? i live in new jersey and i dont know if its a california model
Motorcycle Mechanic: Kenny O., Motorcycle, ATV, Mules, Side by Side's Product Specialist. All Brands replied 8 years ago

Thanks for that info

 

Most likely you model is a 49 state bike since you are on the east coast, synchronizing the carbs does help for idling and acceleration but I don't think that is what you have going on.

 

You should at least think about checking the compression, that can tell you a lot, if the valves haven't been adjusted in a while that is something you should consider also.

 

You might have something going on with the ignition, if you can get yourself a little spray bottle of water, when the bike starts to act up if you can pull over and spray the pipes as close to the head as possible to see if any seem cooler then others, if by chance you had an infra-red heat gum that would be even better yet. What you are trying to determine if any of them are cooler then the others.

 

Now if its dropping two holes then maybe you have a high tension coil failing, since your model utilizes a single pick up coil I don't think that could be the problem.

 

It sounds like its loosing spark, so being able to determine that right now will help tremendously.

 

Also I would like you to try running some carbon cleaner in the fuel, go to a local autoparts chain store, over by the injector cleaner you'll find "Techron" its made by Chevron, if you engine is carboned up real bad sometimes when they get hot the carbon can act like a sponge and absorb the intake charge, run a bottle of that through a tank of gas and see if that helps.

 

Let me know if you have any questions, I'll be glad to answer

 

Kenny

 

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Customer reply replied 8 years ago
okay im gonna check all of this tommorow since it is 2 in the morning over here and ill get back to you
Motorcycle Mechanic: Kenny O., Motorcycle, ATV, Mules, Side by Side's Product Specialist. All Brands replied 8 years ago

Yes its getting late on the westcoast also

 

I'll be here

 

Thanks

Kenny

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Customer reply replied 8 years ago
now ive taken off the valve cover because ive determined it wasnt the spark that was failing i do need to adjust the carbs how would i do so on the 96 katana im an automotive mechanic and the valves on cars have a nut that you use to adjust but on my bike i see no nut to adjust from how would i go about doing so ?
Motorcycle Mechanic: Kenny O., Motorcycle, ATV, Mules, Side by Side's Product Specialist. All Brands replied 8 years ago

Hi thanks for getting back.

 

I didn't get your model but you must have a (N, P, R, S, or a T) model.

 

Its want they call shim on top, on a piece of paper draw 16 circles (8 across and then 8 below) about the size of a half dollar. Then write on the paper which side is exhaust and intake.

 

Position the heel of the cam directly over the shim, so the point of the lobe is 180 degrees opposite of the shim. then measure the clearance and right it down on the paper corresponding for each valve, but before you turn the engine over to measure the next valve slide the rocker over and pop out the shim, there should be a number on the shim, if not (sometimes the number wears off) then you need a pair of digital calipers and measure the shim, (do this measuring in metric) it will be a three digit number like 295, once you obtain that number write it down in that circle with the clearance number. Do this for all 16 valves.

 

I like to measure my clearance in inches, so lets say that my clearance is .006 ~.008 in on the intakes and on my first one I measure .004 (under the spec) and the shim that in that valve right now is a 295, I going to want a 285 shim and that will give me .008 in of clearance.

 

Every .005mm = .002 in of clearance, then reinstall the new shim and MAKE sure you get the rocker slid all the way over and in place.

 

When you measure everything and write it down you can sometimes move shims around to come up with your desired clearance, that way it will minimize the shims you have to purchase, of if your in good with your local Suzuki dealer go back to the service department and maybe he'll swap you out.

 

Let me know if you don't understand something

 

Thanks

Kenny

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Customer reply replied 8 years ago
i cant get the rocker to slide over at all itll move a bit but wont slide over is there something else to it?
Motorcycle Mechanic: Kenny O., Motorcycle, ATV, Mules, Side by Side's Product Specialist. All Brands replied 8 years ago

No that is how you remove the shim, you do see the shim right ?

 

Kenny

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Customer reply replied 8 years ago
i took the bike to my local bike shop and had all the valves adjusted there and still the same problem i notice when it does the problem i can pull out the 4th spark plug and the bike will run the same and i do have spark going to all four cylinders
Motorcycle Mechanic: Kenny O., Motorcycle, ATV, Mules, Side by Side's Product Specialist. All Brands replied 8 years ago

So you have spark, that is good, has anyone check compression across the all four cylinders ?

 

Also it would be a good idea to do a leakdown test if the compression comes up low. Also if compression and leakdown test are OK, then it would likely be in the carb.

 

See you originally said that this looses power when ti get hot, I would thinik that if its something in the carb then that would be there all the time, so I have to say that if you do a compression measurement you will likely find your cause there, then its finding out exactly whats going on in the top end, then a leakdown test will even get you closer to whats wrong.

 

Let me know if you need help with a compression test and or leakdown test.

 

Thanks

Kenny

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