[four_tire]

Hi All,

My Bike suzuki fiero 2002, underwent a rebore and replacement of timing chaing and work on crankshaft. This was because there was white smoke emitting from the silencer, and as known it was due for reboring.

The mechanic recommended that I drive below 40KMS speed for the next 1000 kms and later he would tighten the tappet on the engine..

Although i know about this, but i still dont know why drive it under 40KMS after reboring.. what exactly does happen during that period..

Another question is what are the measures to be taken for a rebore engine..

Hoping to find out

[Technocrat]

See since after re-boring the block is in similar condition as a new one. So you basically need to follow the runin procedure similar to what is needed for a new bike.

[four_tire]

Originally Posted by Technocrat

See since after re-boring the block is in similar condition as a new one. So you basically need to follow the runin procedure similar to what is needed for a new bike.

Okay! what exactly happens to the engine by driving it at 40Kms for 1000 kms?? I mean technically what happens to the engine by doing that

[amit_mechengg]

Originally Posted by four_tire

Okay! what exactly happens to the engine by driving it at 40Kms for 1000 kms?? I mean technically what happens to the engine by doing that

what happens is when u drive at speeds of 40 ( recommended) your moving parts are not strained. the piston and piston rings need to set themselves with your new rebored block, to create good compression. so does the valves and other components

[four_tire]

okay thank Amit and Technocrat.

Another obvious question arises is .. for new engines why doesnt the manufacturer give a tuned i.e. engine which is ready to speed. this will make 100% proper use of the vehicle from the date of delivery

[amit_mechengg]

Originally Posted by four_tire

okay thank Amit and Technocrat.

Another obvious question arises is .. for new engines why doesnt the manufacturer give a tuned i.e. engine which is ready to speed. this will make 100% proper use of the vehicle from the date of delivery

generally the dealer set it to rich mixture so that the engine gets proper lubrication. the engines are properly tuned at the time of delivery. its a misconception that they aren't tuned. what do u mean that they are not tuned for 100% proper use. what proper use are u referring to?

[four_tire]

Originally Posted by amit_mechengg

generally the dealer set it to rich mixture so that the engine gets proper lubrication. the engines are properly tuned at the time of delivery. its a misconception that they aren't tuned. what do u mean that they are not tuned for 100% proper use. what proper use are u referring to?

What i meant by 100% use is ... since it is a new engine and have to run it 1000 kms at 40KMS per hour and hence this means we cant speed. Usually we dont care for speed limit for 150 cc bike till we cross 80KMS etc

Hope you understand what i mean by 100% (not accelarating fully)


Another question i wanted to ask is, if the more lubrication can help the bike.. should i try adding some engine oil directly with petrol (as we do in case of 2 stroke engines). Will doing this to 4 stroke engines help or hamper it.

[Sankar]

Originally Posted by four_tire

Okay! what exactly happens to the engine by driving it at 40Kms for 1000 kms?? I mean technically what happens to the engine by doing that

The piston rings and the the bore hone has to wear each other out to a limit to make a perfect sealing. At this stage every metal component inside the engine wear each other out and bed in to a perfect running tolerance.

And a new bore is usually done tight to a specific clearance from the factory, and 'tighter' in case of rebores done by most mechs. If you over revv a new engine that is tight it over heats and the piston grows and it gets stuck in the bore. And you'll again visit your mech telling him that the engine seized.

It's to avoid such situations that your mech asks you to do a run in at 40 for 1000km. But if you complete the run in at 40 and take her to 100kmph at the 1001ths or 1050th km there is a good chance that it will seize. becuase getting the run in completed at 40kmph is not right technically.

if you follow this link you'll understand why. Eventhough it's a Bullet page the technicalities holds good for most engines.

The Bullet: Mystries & Myths - Running-in a new Bullet

[four_tire]

Hey Sankar, that was a very informative, thanks.

but what did you mean by saying this here...

Originally Posted by Sankar

becuase getting the run in completed at 40kmph is not right technically.

[amit_mechengg]

u run at 40 KMPH for 1000 kms. dont worry. those specs have all tolerances in them.