Question about Honda CB 750 Nighthawk Motorcycles

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Carburetor problem or ? 1975 Honda CB750K, #4 Cylinder about 160 degrees F cooler than other cylinders. Compression all about 135 psig, overhauled the carbs fuel in bowl is clear and levels are #1 & #3 is 45ml (1.5 oz), #2& 4 is 40 ml (1.4 oz) Used a Fluke non contact thermometer and got the following temperature on fin at 12:00 position above exhaust pipe, outside temperature was 25 degrees C ( 77 degrees F), bike brought up to temperature and at idle not moving #1& 2 read 134 degrees C (273 degrees F) #3 read 132 degrees C (270 degrees F) #4 read 44 degrees C (111 degrees F) Checked spark and was strong, has an electronic ignition system HELP very little hair left?

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Be certain that fuel is getting into the float bowl on the bad carb. If so, and the fuel level is at the correct height, the problem would be either the slide is not raising as it should, the main jet is plugged up or there is a blockage in the air clearer/manifold.
The compression is good so a valve can't be stuck. You said you have spark. The only thing left is a fuel problem or air problem. Please rate my answer. Thanks.

Posted on Aug 19, 2010

Testimonial: "Thanks I will check the slide and air manifold"

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Just fixed a similar problem on my '77 GS750. No temp gauge, but one cylinder was cooler than the rest (spit test!). Turned out to be simply a duff HT Cap. I had also checked the spark, but it looked as 'blue' as the others.
I would also check the temp on the downpipe for each cylinder as this would eliminate any issues with the thickness of the fins/heat path etc.
Does the bike run well?
Hope yours is as easy to fix as mine!

Posted on Aug 19, 2010

Testimonial: "I will check high tension leads, bike does run fine"

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96 Honda Civic making a popping noise when I release the clutch and third gear


Reasons for popping noise:
Popping noise could occur due to the malfunction in the ignition system, leaky valves, weak cylinder compression, carbon accumulation in the combustion chamber or lean fuel.
1. Ignition system malfunction (Misfire).
Check:
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My boat motor has low compression @ number 1 cylinder how can I fix it


2 possibilities:
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-2 Your cylinder has seized. If it's the upper cylinder, you'll have also to check your cooling system! Look at your spark plug if you can't see some 'aluminum' deposit on it. Or, inspect the inside of that cylinder with an endoscope.
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Low overall compression in 1996 honda accord 4cyl 129.75 psi avg.


the compression pressures are on the low side. The indications are worn rings as the pressure readings come up when the ring seal is improved with the addition of oil. The bores will be worn in a taper and if the head was to come of there would be a noticeable lip where the top ring stops in the cylinder
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if there is an oil consumption problem( smokey) then yes
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1975 honda tl 250 runs hot and lean


Hi, Anonymous and the usual suspects are:
1. Engine oil level and SAE weight are too low or not circulating.
2. Insufficient or blocked air flow over the engine.
3. Heavy combustion chamber carbon deposits.
4. Ignition timing retarded due to faulty MAP, CKP, or CMP sensor.
5. Carburetor jetted too lean.
6. Leaking intake or exhaust valve.
7. Water coolant old or low change every two years.
8. Water pump failure.
9. Radiator clogged, cap loose or malfunctioning.
10. Radiator fans not coming on.
11. Clutch slipping, brakes dragging, heavy load, towing a trailer etc.
12. Idling too long without moving.
13. For constant hot weather temperatures, mountain, or desert riding conditions consider adding an oil cooler and or cylinder head cooler.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below. Good luck and have a wonderful day.
http://www.thebookishblog.com/1975-1976-1977-honda-tl250-tl-250-service-shop-repair.pdf
http://www.partsfish.com/page/oem-parts-for-honda
http://mybikemanuals.com/honda/honda-tl-owners-manuals
From 1975 to 80
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1 Answer

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Remember the important thing is to find compression readings that are very close to each other. I have an '87 Sentra with 75,000 miles(true!)-lowest comp. is 160, highest is 165 psi-runs great, good power. Also a '79 Datsun pickup (with god only knows how many miles-about 200,000 maybe). Compression is about 125-135 psi, fairly well balanced-noticeable loss of power, very little oil burning, still runs fair to good-dependable, at least.
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1 Answer

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2. Insufficient or blocked airflow over the engine.
3. Heavy combustion chamber carbon deposits.
4. Ignition timing retarded due to a faulty MAP, CKP, or CMP sensor.
5. Carburetor jetted too lean.
6. Leaking intake or exhaust valve.
7. Clutch slipping, brakes dragging, heavy load, towing a trailer.
8. Idling too long without moving.
9. Constant hot weather temperatures, mountain, or desert riding conditions consider adding an oil cooler and or cylinder head cooler.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below. Good luck and have a wonderful day.
77 gl1000 overheating problem GL1000 Information Questions goldwingdocs com
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Honda GL 1000 Shop Manual
https://www.partsfish.com/page/oem-parts-for-honda
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Oct 15, 2009 | Honda CB 750 Nighthawk Motorcycles

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