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Engine difference – 3TB vs 4PT Engine difference – 3TB vs 4PT
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Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
Photo by George Guille, It's going to be a long 300km... Bolivian Amazon

I haven't been everywhere...
but it's on my list!


Photo by George Guille
It's going to be a long 300km...
Bolivian Amazon



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  #16  
Old 17 Apr 2016
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I found different combustion chamber sizes on the older bikes when the hp ratings changed , could very well be they opend them up a bit more or made the ports a little different size , doesn't take a whole lot if done to the right places. A person would need to have one of each head side by side and measure all aspects.
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  #17  
Old 18 Apr 2016
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My 2003 model dynoed 34,6hp on the rear wheel with the snorkel removed, and a new exhausttip, and i think a pipercross airfilter. At that point it had over 50.000km on it, so perhaps the powermods just about made it up for the wear in the engine...

My friends ktm640 dynoed with a 10hp loss from the stated HP at the crank, to the actual meassured rearwheel-hp. If it's the same for the xt600, you would be very close to 45 hp on the crank
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  #18  
Old 18 Apr 2016
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True Rear Wheel Horsepower

The SRX is the same engine. Who knows, maybe its all in the exhaust, maybe you got the 44hp when open up with more air and new exhaust.
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  #19  
Old 9 May 2016
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Valve shrouding
On my 2001 E , the valves were badly masked by the sides of the combustion chamber even at full lift. I marked around the head gasket and opened the head away from the valves. It made a real difference.
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  #20  
Old 9 May 2016
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Quote:
Originally Posted by frozenbiker View Post
On my 2001 E , the valves were badly masked by the sides of the combustion chamber even at full lift. I marked around the head gasket and opened the head away from the valves. It made a real difference.
Ok, so what you mean by badly masked? BTW i tested a 4pt with leo vince against 3tb and it seems similar, in my head it should have been a much bigger difference so i bet the exhaust makes less hp or it never was any less output on the 4pt.
Last edited by xtrock; 9 May 2016 at 10:28.
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  #21  
Old 9 May 2016
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He means the combustion chamber is closed over somewhat around the outside in a portion of the valves , valves can't "breath" fully. Think roof. The XT's aren't that bad , similar to most . The head gasket need to be shaped so they don't stick into the combustion chamber. My klx650's are horrible and 6-8hp gains can easily be had by going 2mm overbore and grinding the chamber open around the outside of the valves to match the 2mm bigger bore.

I haven't seen any of the newer heads to know if they changed the shape , that could easily loose several hp.
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  #22  
Old 9 May 2016
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danimalu if you remove head again you can take a picture.
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  #23  
Old 11 Jun 2016
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Has the 3tb a big valve head ?

Cheers
Min
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