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Hi Team,
I have been scratching my head over this problem.
Being a Yamaha (2 stroke) lover, I managed to buy this beast. Its a 2002 make, running 47k on odo. Stock condition engine with a standard size piston.
After I became the 2nd owner for this beast, I decided to give a complete cosmetic touch-up - which I got done after spending few thousands.
The engine seems alright, except the problem of "jerking". I thought this problem will be killed after I give her a good service, but its still there
Being keen enough to restore my bike and not to lose any parts - I got all the work done under my supervision (infact brought the engine stock at home while the bike remained dismanteled in the workshop).
My intention is to have this machine in stock condition as long as I am alive, and thats the reason struggling to get all the bits together.
I am a good rider and have this bike as a commuter (30 KM approx use/day). Hardly cross speed of 60 Kmph, and mostly stick to the economic range of 40-50 Kmph
Problems:
1. At any gear position, when I go over a certain speed (say 10 - and high) and close the throttle, she behaves very weird. I mean the deceleration is not smooth at all.
It gives heavy jerks as if someone is pulling and then pushing the bike while the throttle is closed. So to get rid of this, I pull the clutch and then it gives a momentory relief. And this continues untill she comes down to 20. Thought this was a clutch related problem so got the OE pressure housing and also removed the play in the clutch bell and also got the new rubber dampners installed. But no use.
Is this a damaged piston which is causing this, or the exhaust port covered with carbon ? Never got the silencer decarbonized.
The head was cleaned and the piston as well before the assembly.
My mechanic suggested to change the reed valve, but I wonder this will resolve the problem as the reed valve is a vibratory unit which is to provide better AF mixture to the cylinder.
can this be a ignition timing problem, may be its delayed
2. The biggest problem - I have blewed up 4th spark plug in mere 300 Km of run. It initiated with the starting problem. Then took her down to the mechanic and saw the spark plug. The plug had life, so got it cleaned and installed back. The bike started fine. But I identified that the spark plug was black in color as if dipped in the oil. I know this is not a good sign. But gave it a try. And it worked well another couple of days. And one fine day the bike got off while at 50 Km/hr.. bhuurrrrr bhurrr.. and that's it - engine cut off. I had to get the plug changed. Now this new one lasted for another 60 Km's. Again it was fouled. Got a new one installed and so on... Every time the engine gets too hot after around 10 Kms of run and I see that the color of the electrode is not reddish neither it is dry. Its black. (Plug type - MICO BOSCH)
IIs this due to worned piston rings - am I correct on this as I guess this is the predominant source of leting the oil uptil the spark plug.
And also the bike smokes more. I understand that these machines are meant for smoking, but comparatively its more.
2T oil - Castrol
The carb is tuned to have economic mixture which is not that rich.
I am running on AUTOLUBE.
3. When I try to maintain a constant throttle on the highways, say if I am maintaining 45 Kmph, the engine tends to lose power and I feel that the fuel flow is not constant and can hear that lag in the sound. So to again maitain the speed to 45, I slightly overcome the lag with the slightly extra throttle.
Is there something wrong with the carb jets ?
Can this be rectified by disassembling and cleaning the carb thoroughly again and install the components like needle throttle valve, main and pilot jets which comes in a NATCO carb repair KIT ?
Is NATCO carb repair kit alright ? Can this kit give me a mileage of around 38-40 KMPL ?
Well I guess the bore has lost its compression now (never got a compression test done though) but the below said factors are observed:
- Ring /abnormal sounds from the cylinder.
- Throttle response is OKAY - but it is not that good.
- Mileage 25 KMPL.
Well, as this problem is related to much of the engine and its associated parts, I would like to tell you that I have replaced the below parts:
(All genuine Yamaha parts):
Clutch plates and pressure plates
OE Clutch seal
OE air filter
All cables
Harness
clutch Rod
carburetor manifold.
Clutch pressure housing.
Never thought I would need anything else apart from the ones mentioned above to get this bike running smoother. But I guess I was wrong.
Could the experts here in this forum please advice and guide me which string of this machine shall be touched so as to get her back to smoother life.
I have enquired about the piston rings, but could not procure one - as most of the dealers say that the rings come in a set with the piston kit. If piston rings are the main culprits then could you please suggest any source to purchase the piston rings alone.
I am from Chennai.
The reliability has come into question now and there is only one question in my mind when I go to bed everyday, how do I rectify these problems.
DOCTORS - Please shed some expertise. . I am really waiting eagerly to sort this problem.
Many thanks
I have been scratching my head over this problem.
Being a Yamaha (2 stroke) lover, I managed to buy this beast. Its a 2002 make, running 47k on odo. Stock condition engine with a standard size piston.
After I became the 2nd owner for this beast, I decided to give a complete cosmetic touch-up - which I got done after spending few thousands.
The engine seems alright, except the problem of "jerking". I thought this problem will be killed after I give her a good service, but its still there
Being keen enough to restore my bike and not to lose any parts - I got all the work done under my supervision (infact brought the engine stock at home while the bike remained dismanteled in the workshop).
My intention is to have this machine in stock condition as long as I am alive, and thats the reason struggling to get all the bits together.
I am a good rider and have this bike as a commuter (30 KM approx use/day). Hardly cross speed of 60 Kmph, and mostly stick to the economic range of 40-50 Kmph
Problems:
1. At any gear position, when I go over a certain speed (say 10 - and high) and close the throttle, she behaves very weird. I mean the deceleration is not smooth at all.
It gives heavy jerks as if someone is pulling and then pushing the bike while the throttle is closed. So to get rid of this, I pull the clutch and then it gives a momentory relief. And this continues untill she comes down to 20. Thought this was a clutch related problem so got the OE pressure housing and also removed the play in the clutch bell and also got the new rubber dampners installed. But no use.
Is this a damaged piston which is causing this, or the exhaust port covered with carbon ? Never got the silencer decarbonized.
The head was cleaned and the piston as well before the assembly.
My mechanic suggested to change the reed valve, but I wonder this will resolve the problem as the reed valve is a vibratory unit which is to provide better AF mixture to the cylinder.
can this be a ignition timing problem, may be its delayed
2. The biggest problem - I have blewed up 4th spark plug in mere 300 Km of run. It initiated with the starting problem. Then took her down to the mechanic and saw the spark plug. The plug had life, so got it cleaned and installed back. The bike started fine. But I identified that the spark plug was black in color as if dipped in the oil. I know this is not a good sign. But gave it a try. And it worked well another couple of days. And one fine day the bike got off while at 50 Km/hr.. bhuurrrrr bhurrr.. and that's it - engine cut off. I had to get the plug changed. Now this new one lasted for another 60 Km's. Again it was fouled. Got a new one installed and so on... Every time the engine gets too hot after around 10 Kms of run and I see that the color of the electrode is not reddish neither it is dry. Its black. (Plug type - MICO BOSCH)
IIs this due to worned piston rings - am I correct on this as I guess this is the predominant source of leting the oil uptil the spark plug.
And also the bike smokes more. I understand that these machines are meant for smoking, but comparatively its more.
2T oil - Castrol
The carb is tuned to have economic mixture which is not that rich.
I am running on AUTOLUBE.
3. When I try to maintain a constant throttle on the highways, say if I am maintaining 45 Kmph, the engine tends to lose power and I feel that the fuel flow is not constant and can hear that lag in the sound. So to again maitain the speed to 45, I slightly overcome the lag with the slightly extra throttle.
Is there something wrong with the carb jets ?
Can this be rectified by disassembling and cleaning the carb thoroughly again and install the components like needle throttle valve, main and pilot jets which comes in a NATCO carb repair KIT ?
Is NATCO carb repair kit alright ? Can this kit give me a mileage of around 38-40 KMPL ?
Well I guess the bore has lost its compression now (never got a compression test done though) but the below said factors are observed:
- Ring /abnormal sounds from the cylinder.
- Throttle response is OKAY - but it is not that good.
- Mileage 25 KMPL.
Well, as this problem is related to much of the engine and its associated parts, I would like to tell you that I have replaced the below parts:
(All genuine Yamaha parts):
Clutch plates and pressure plates
OE Clutch seal
OE air filter
All cables
Harness
clutch Rod
carburetor manifold.
Clutch pressure housing.
Never thought I would need anything else apart from the ones mentioned above to get this bike running smoother. But I guess I was wrong.
Could the experts here in this forum please advice and guide me which string of this machine shall be touched so as to get her back to smoother life.
I have enquired about the piston rings, but could not procure one - as most of the dealers say that the rings come in a set with the piston kit. If piston rings are the main culprits then could you please suggest any source to purchase the piston rings alone.
I am from Chennai.
The reliability has come into question now and there is only one question in my mind when I go to bed everyday, how do I rectify these problems.
DOCTORS - Please shed some expertise. . I am really waiting eagerly to sort this problem.
Many thanks
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