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Old 8th December 2012, 19:15   #46
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Interesting thread and very much required for me now .
A couple of days back, I had started my CD 100 SS, 1993 model which is very rarely used at my native place . I was pretty happy that the bike started after 2 long years of continuous non usage . I was happy that the bike started and I used it for one full day without any issues . The second day the issue started and the bike never started . The kicker went down without any force , I initially thought it should be a clutch plate problem but I could never start the bike . Later consulted a mechanic who tried all possible things by checking spark plug, cleaning carburetor, jet etc . But nothing happened and finally he declared the compressor had failed and also the piston rings should be replaced . Even though the bike is of 1993 model but still I think maximum only 50k kms should be the odo reading . Guy's please advice me whether it would be worth doing this job for my old bike or simply go for a new bike keeping the fact in mind that very rarely the bike will be used and an old bike may give more troubles .

Last edited by rki2007 : 8th December 2012 at 19:17.
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Old 19th May 2015, 23:52   #47
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Default re: Honda Unicorn losing Engine Compression - HELP

Bumping an old thread.

Dear BHPians,

Facing a peculiar issue in my 2006 Unicorn. Bike has done 25.5k till date with engine oil replaced every six months (or before 1500 km, whichever is earlier). Bike is giving a peculiar tik tik sound when ridden for prolonged times i.e. > 30 minutes and it surprisingly vanishes once the engine cools down. The vibes are transmitted to the seat (may be plastics have started showing their age).

Bike reaches to higher double digits easily, sprocket set and spark plug has been replaced as precautionary measure. Engine oil level is Ok. Sometimes bike switches off when throttle is released but comes back to life on pressing self starter. Cold engine RPM hovers around 1-1.3k.

RPM needle is not flutuating. Bike is not emitting any black/white smoke, clutch is perfectly fine and kick starter is also working normally. Mechanic says Valves rings and Piston needs replacement . The tip of spark plug was black in colour and was cleaned using petrol for the time being. Other mechanic says timing chain needs replacement. I feel the engine heat has also increased over time.

Kindly suggest what could be the root cause of this problem.
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Old 20th May 2015, 14:10   #48
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Default re: Honda Unicorn losing Engine Compression - HELP

Don't worry at all. The noise you are mentioning is sound coming from the silencer after you park it and IIRC it comes from the catalytic converter and is pretty normal. I wonder why you didn't notice it earlier.
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Old 20th May 2015, 14:28   #49
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Default re: Honda Unicorn losing Engine Compression - HELP

Quote:
Originally Posted by abhipuri View Post
Facing a peculiar issue in my 2006 Unicorn. Bike has done 25.5k till date with engine oil replaced every six months (or before 1500 km, whichever is earlier). Bike is giving a peculiar tik tik sound when ridden for prolonged times i.e. > 30 minutes and it surprisingly vanishes once the engine cools down.
This sound is probably due to loose tappets. Adjust your tappets and this sound should be gone. Try and find a mechanic who will do this tightening using a feeler gauge and not sleight of hand. Because margins are as narrow as 0.07mm being too much clearance, 0.06mm just right and 0.05mm too little. It is nearly impossible to get this right with bare hands.

The timing chain will not need replacement this early. My bike has done 38k km without needing a timing chain replacement. 25.5k km is too early for that.

Quote:
Originally Posted by abhipuri View Post
Sometimes bike switches off when throttle is released but comes back to life on pressing self starter. Cold engine RPM hovers around 1-1.3k.
Do you also face issues with idling and light throttle inputs after idling for some time?

You might have a clogged slow jet in your carburetor. This can be sorted out in a matter of a minutes.
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Old 20th May 2015, 15:59   #50
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Default re: Honda Unicorn losing Engine Compression - HELP

Quote:
Originally Posted by abhipuri View Post
Bumping an old thread.

Mechanic says Valves rings and Piston needs replacement . The tip of spark plug was black in colour and was cleaned using petrol for the time being. Other mechanic says timing chain needs replacement. I feel the engine heat has also increased over time.

Kindly suggest what could be the root cause of this problem.
Symptoms for Valve rings & piston change are :

1. Visible smoke emitting from exhaust.
2. Lack of power in the bike as in you will feel the engine being stressed.
3. Loss of compression which is the important symptom. The engine sometimes in running switches off and won't start. Try starting through kick start you won't feel any hardness as it becomes very loose.

Hope this helps.
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Old 22nd May 2015, 13:21   #51
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Default Re: Honda Unicorn losing Engine Compression - HELP

Quote:
Originally Posted by abhipuri View Post
Bumping an old thread.

Dear BHPians,

Facing a peculiar issue in my 2006 Unicorn. Bike has done 25.5k till date with engine oil replaced every six months (or before 1500 km, whichever is earlier). Bike is giving a peculiar tik tik sound when ridden for prolonged times i.e. > 30 minutes and it surprisingly vanishes once the engine cools down. The vibes are transmitted to the seat (may be plastics have started showing their age).

Bike reaches to higher double digits easily, sprocket set and spark plug has been replaced as precautionary measure. Engine oil level is Ok. Sometimes bike switches off when throttle is released but comes back to life on pressing self starter. Cold engine RPM hovers around 1-1.3k.

RPM needle is not flutuating. Bike is not emitting any black/white smoke, clutch is perfectly fine and kick starter is also working normally. *Mechanic says Valves rings and Piston needs replacement . The tip of spark plug was black in colour and was cleaned using petrol for the time being. Other mechanic says timing chain needs replacement. I feel the engine heat has also increased over time.

Kindly suggest what could be the root cause of this problem.

I am repairing a Hero Honda Street which has been in storage for a year.

The bike stops when the throttle is opened. This is a classic case of lean mixture because of air entering the system or fuel starved at main jet.

I took it to a mechanic who was working on another bike. He came over and suggested I change the plug. I don't have time to argue with them and go along because it's a cheap fix. After plug change the spark is weak. He suggests I leave the bike.

Big mistake.

I return and the spark is blue and fat, and he explains he has changed the coil, showing me an old coil. Total bill 400 rupees. This could have been fixed by cleaning and resetting the points.The bike still shuts down at full throttle. He suggests we change the carb. I refuse.

The next day, I go to another mechanic who is sitting outside his shop. He sees the problem and suggest I leave the bike. I refuse.

He removes the carb and finds the spacer between the carb and the intake elbow cracked. He replaced the spacer.

Problem solved.

Moral of the story 1:

Don't leave the bike behind.

Before these two visits other mechanics have suggested I change the clutch (centrifugal clutch grabbing at full throttle claimed, but the clutch releases properly at low rpm!) change the rings (compression loss claimed, but no blue smoke, a sign of oil burning from worn rings! Ditto valve guide wear.)

Moral of the story 2:

Know some common engine faults and reasons for those faults. Else they will fix your problem with a spacer change and show you a set of old valves, piston or rings and bill you for a major overhaul!

Last edited by proton : 22nd May 2015 at 13:30.
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Old 24th May 2015, 12:17   #52
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Default Re: Honda Unicorn losing Engine Compression - HELP

Quote:
Originally Posted by kkg View Post
Don't worry at all.......
Thanks buddy, actually noise is coming while the bike is running.

Quote:
Originally Posted by ashwin.terminat View Post
This sound is probably due to loose tappets.....
......
25.5k km is too early for that.
Need to get hold off a good mechanic in Lucknow.


Quote:
Originally Posted by ashwin.terminat View Post
Do you also face issues with idling and light throttle inputs after idling for some time?

You might have a clogged slow jet in your carburetor. This can be sorted out in a matter of a minutes.
Yes, this does happen sometimes. I have good the carburetor cleaned during my last servicing (2 months and ~1300 km back).
Can bad quality of fuel be a possible culprit? Will cleaning the tank help in this case; If yes, Do I need to get the tank removed or any additive can take care of this? Asking this because I am new in this town.

Quote:
Originally Posted by Abhi_abarth View Post
Symptoms for Valve rings & piston change are :

1. Visible smoke emitting from exhaust.
2. Lack of power in the bike as in you will feel the engine being stressed.
3. Loss of compression which is the important symptom. The engine sometimes in running switches off and won't start. Try starting through kick start you won't feel any hardness as it becomes very loose.

Hope this helps.
Thanks for the detailed explanation.
Engine did switch off once while riding continuously for > 1 hour. Hope it is nothing serious.
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