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Old 11th February 2010, 17:15   #1
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Default Pulsar 150 DTSi - Valve bent! Help needed

Hey guys, I need help here.

I own a pulsar 150 digital, 3 years old, 18000 kms. Today afternoon the bike stalled on a intersection and refused to restart. I took it to nearest authorized service center, where the mechanic told me my valve are bent. I am totally . How can a well maintained, low on mileage, gently run bike get the valve bent? Mechanic told me pulsar has very thin valves, hence it is a common problem. Has anyone faced similar problem in pulsar? Is the mechanic right?

I have loved the pulsar since it was launched in 2000. That is why when i could i went for this bike. I always knew bajaj has some quiality issues, but this is absolutly rediculous.
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Old 11th February 2010, 17:19   #2
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I found my 'zma's valve bent with barely 15K
as per mechanic-bad fuel...
whereas everyone swears from where i filled fuel, its a company owned and operated BP pump and i filled only Speed 93 and yes, my oil change interval was 1000kms...

get the valves changed, that is the only option left
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Old 11th February 2010, 17:30   #3
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Get thevalve changed. How it can happen is a good question which only experts can say.My pulsar is 5 year old and has run 60k kms and not faced anything like this. So all the best in the quest to get the answers and for knowledge improvement for us also.
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Old 11th February 2010, 17:39   #4
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Quote:
Originally Posted by indianvirus View Post
Mechanic told me pulsar has very thin valves, hence it is a common problem. Has anyone faced similar problem in pulsar? Is the mechanic right?

I have loved the pulsar since it was launched in 2000. That is why when i could i went for this bike. I always knew bajaj has some quiality issues, but this is absolutly rediculous.
1) Its not common issue with Pulsars. In college I have seen many pulsars do more kms without any issue. And the biggest problem with Bajaj is gearbox, not valves. Gearbox is Achilles heels for Bajaj, but not engine. And rather than lack of engineering or poor quality, its the A.S & S. that eventually spoils all the things. My friend's Pulsar was given for service, they forgot to put the lid back after changing engine oil, so the oil was slowly but steadily coming out from where it is supposed to be poured and engine seized.

2) Its bad fuel that has most probably caused you this problem. I think earlier in Pune because of bad fuel many had faced this issue of valve. But there, both Bajaj and HH came up with some scheme or some discount.
The only option that you are left with is to replace the damaged part.
Be firm when you visit any service center of Bajaj. I have very bad experience, both at A.S motors and BAC.

I had fight with Mr. Chirag Shukla who was service manager ( dont know where he is or what is his designation ), but beware of him, he will make you lose your temper, and can fight for millions of years.
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Old 11th February 2010, 17:46   #5
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I agree with quality standards of AS motors and BAC. Both are always eager to void your warranty. You do anything with the new bike and they say it will be difficult for you to claim warranty.
As far as fuel is concern I live around makarpura, so i am getting it filled where it feels better. But I am not very sure fuel quality at these better places now.
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Old 12th February 2010, 17:15   #6
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I own a 150dtsi 2005 make (alloys / analog speedo). Ive done more than 34K Kms on the bike. I am not a gentle rider at all, quick acceleration and average highway speed of 85-95 kmph. I've never even changed the clutch plate any time, leave alone the valves.
Get the bike checked from another mechenic.
Pulsars need regular oil change, I do it every 2.5k - 3K kms. The only parts I need to replace are the brake liners.
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Old 12th February 2010, 17:28   #7
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Quote:
Originally Posted by aaggoswami View Post
1)
2) Its bad fuel that has most probably caused you this problem. I think earlier in Pune because of bad fuel many had faced this issue of valve. But there, both Bajaj and HH came up with some scheme or some discount.
The only option that you are left with is to replace the damaged part.
Be firm when you visit any service center of Bajaj. I have very bad experience, both at A.S motors and BAC.
How does the use of bad fuel bend the bike's valves? Simply not possible. If the valve is indeed bent the valve must've hit something.
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Old 12th February 2010, 17:34   #8
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Quote:
Originally Posted by Sankar View Post
How does the use of bad fuel bend the bike's valves? Simply not possible. If the valve is indeed bent the valve must've hit something.
+1. I had the same question... Anyone who can explain?
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Old 13th February 2010, 18:49   #9
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bad fuel can cause knock and detonation, this may be the reason why the valves are bent
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Old 13th February 2010, 19:45   #10
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Engine detonation is not enough to bend the valve stem. Unless excessive detonation breaks/hole the piston and resulting junk get in the way. But still bad fuel will not cause that much damage unless timing or afr is off.
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Old 13th February 2010, 23:03   #11
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Quote:
Originally Posted by Sankar View Post
Engine detonation is not enough to bend the valve stem. Unless excessive detonation breaks/hole the piston and resulting junk get in the way. But still bad fuel will not cause that much damage unless timing or afr is off.
Quote:
Originally Posted by mithunmiranda View Post
bad fuel can cause knock and detonation, this may be the reason why the valves are bent
Quote:
Originally Posted by MurtazaGhiya View Post
+1. I had the same question... Anyone who can explain?
The reason is as mentioned by mithunmiranda. This was told to me by Bajaj A.S.C also. Did try to google around it, but did not help. In case of bikes, the tolerance limits are not as high as that of automobiles was one more reason that was stated.

This happens due to repeated use of bad fuel for a long time. The misfires damage the valves a bit. Another problem is the back stroke or back fire. A This happens due to bad fuel, leading to higher damage.
I knew a few Caliber that faced this issue of first back fire and then valve problem.

Last edited by aaggoswami : 13th February 2010 at 23:08.
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Old 13th February 2010, 23:18   #12
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Quote:
Originally Posted by aaggoswami View Post
The reason is as mentioned by mithunmiranda. This was told to me by Bajaj A.S.C also. Did try to google around it, but did not help. In case of bikes, the tolerance limits are not as high as that of automobiles was one more reason that was stated.

This happens due to repeated use of bad fuel for a long time. The misfires damage the valves a bit. Another problem is the back stroke or back fire. A This happens due to bad fuel, leading to higher damage.
I knew a few Caliber that faced this issue of first back fire and then valve problem.
Sorry, detonation does not destroy valves just like that.
If valve has to bend valve has to hit metal.
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Old 14th February 2010, 16:58   #13
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sticky valve guide &/ lubing issues, loading the valve stem to cause gradual bending ?
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Old 18th February 2010, 22:20   #14
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Default Reasons for valve bend

Valve bends usually occur in ghat sections specially for 100cc and less bikes.
1st Reason: Due to load on the engine during steep climbs the engine has to work a lot and gets heated. This heat increases the temperature of the valve (exhaust valve) to a extent that the metal softens to the extent that it is easily susceptible to permanent deformation.Now the valve is brought back to its original position by the hard valve spring so it makes the hot valve bring back to its seat which is in a way a hammering action enough to permanently change or bend the valve.I myself experienced this on a steep up hill and landed up changing my valve.
2nd reason which is rare but does happen: The valve spring has a inertia of its own and takes a finite time to bring the valve back to its seat. If the rpm of the engine is quite high the spring doesnot get enough time to bring back the valve to its seat and before the valve can come back to its seat the fast approaching piston comes up and bangs the valve bad enough to break valves,pistons,break connecting rods and in severe cases enough to make the connecting rod break the crank case and come out.(All these cases might not hold true to indian motorcycle engines 100ccto250cc but surely hold true to engines of tractor,4 wheelers).The engine rpm can shoot quite high in lower gear and steep slopes downhill.
3rd reason: A engine which is tuned for mileage or a lean burn engine runs hot because the piston is compressing more air and less fuel to give sufficient down force on the piston. The engine acts more like a air compressor than an engine and so gets hot.Its because due to less fuel particles the latent heat of vapourisation of the fuel particles (which brings the working temperature down) is also less and the engine runs hot.
This hot running engine is also one of the cause of the valve neck softening due to higher working temperatures leading to valve bend.
4th reason: Manufacturing defect in the valve.

My personal opinion is that Pulsar engines run hotter than other engines due to twin sparkplugs and therefore are more susceptible to heat associated failures.

Solution: Replace Valve,replace valve seat if required or get it ground to make a effective seal with the new valve and also check the valve guides for leakage-if found replace it.
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Old 24th February 2010, 23:49   #15
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Thank you very much sirji for awesome explanation, really appreciate it.

But none of above really is applicable to my bike. I live in baroda so no ghats around. I ride very gently, so no high rpm or blazing trips. It happened while commuting at 40 kmph. I change oil regularly, get the bike serviced periodically, wash it every week. And it happened after 3 years of ownership so cannot be manufacturing defect.

I guess it purely hard luck, what else?
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