Nov 13, 2008 12:47 PM
15140 Views
(Updated Jul 01, 2010 11:05 AM)
Pulsar with charismatic heart - (engine modified to 66*56.4 mm bore * stroke dimension ) Oversquare engine.
I have a pulsar 150 dtsi 2004 model. The bike had done around 36000 kms and running nicely. It had no issues. I just wanted to de carbonize the engine and enhance the performance and efficiency. I knew a mechanic near my house (Ganesh)who is good at engine modification/restoration kind of work.
One fine day took my vehicle to his garage. He suggested me to go for a engine over haul. So we decided to dismantle the engine and found a good amount of carbon deposit in the cylinder head, valves, piston etc. He suggested to get the engine rebored, the inlet and exhaust ducts machined / polished with slightly higher diameter. This enhances fluid flow to and out of the cylinder. Adding to this he suggested to go for new pistons and valve sets. I had a wild thought of going for increasing the cubic capacity of the engine. So we discussed and I gave him a free hand to experiment.
After two days I got a call from him saying that we can try Karizma's (Hero honda) piston and bore. I gave him the green signal and after a day we got the engine head and body rebored to accomodate the bigger bore of karizma and new karizma piston (original bore of pulsar stands at 57 mm diameter against the karizma bore at 66mm).
He assembled the engine which took another whole day. And now my engine has 66mm (bore) and the stroke remains unchanged at the original dimension of 56.4 mm (stroke) which translates to 192.86 cc close to the pulsar 200 dimensions :)
The cost of machining came to 3250 Rs (INR). This includes the reboring, new karizma piston, valve setting, crank / connecting rod resetting (because my original connecting rod had a minor shake), head polishing, inlet and exhaust ducts machining for enhanced fluid flow etc.
Spare parts costed around 3500 Rs. Totally it costed me around 8000 Rs including labour charge. This overall cost could vary based on your existing engine parts condition whether we can reuse existing parts or have to go for certain replacements.
Just got the vehicle done yesterday and now its in the run in period so am driving carefully keeping the engine revs below 4000 rpm. I can feel the difference in power.
The end result is a over square engine . A over square engine (like the one offered in Apache RTR 160 bike) is an engine with the bore (diameter of engine cylinder) size being more than the stroke (cylinder length or piston travel distance). Over square engines are known for enhanced power and slightly lower torque. They can run at higher rpms than square or undersquare engines.
Overall engine efficiency will be good with slight reduction in mileage. I can give a better detail after the run in period or after the vehicle has run in around 1500 kms.
The expert who did this is Ganesh , the mechanic from Munnekolala, Marathalli, Bangalore.
You can contact him on 9964839731
He is not so well conversant in English but can communicate in Hindi, Kannada, Telugu and Tamil.
FREE FLOW EXHAUST - UPDATED ON 1ST JULY 2010
I wanted to try free flow exhaust. So I consulted with Ganesh. He suggested to alter the existing exhaust assembly and convert it to free flow. It was done by one of his friends and costed around 1000 Rs. Now the sound is completely changed, there is a deep throat rumble from engine. Its awesome. The low end torque of engine has increased nicely. I could use 5th gear at speeds of 25 km to 30 km despite using a overall tall gear ratio (since I use a 36 teeth rear sprocket and original sprocket of pulsar has 42 teeth).
