Engine difference – 3TB vs 4PT (missing 5 HP)
 

The 3TB model is supposed to be 33KW, but the newer 4PT is 29,4KW. Has it really 3,6KW less or is Yamaha just using different numbers for some reason? Anyone know??

FYI:
I have the 4PT model. For testing purposes I did take out the airbox snorkel and the muffler tip (I would not run the bike like that though, too noisy) .

Now the bike was more noisy but to my surprise I could not feel any power difference. The bike did not feel lean. Most bikes with heavily restricted intake/exhaust respond quite a lot to even modest “decorking”.

Yes its correct the new model has less bhp.

Ok, thanks. Do you know why?

I'm wondering if the 4PT can be upgraded to 3TB specs by swapping out parts.. The basic engine is more or less the same except for the clutch I am told.

Carb, exhaust making the difference? just my guess.

Check the intake boot inside diameter, the one that bolts to the motor. It is supposed to be smaller dia, so an old version will help.

Thanks guys.

I did compare part numbers (intake boots) and they seem to be the same. Maybe I will take it apart anyway, and take a look.

My last XT has a 4PT engine and a ´95 TT600S carb and everybody said that XT runs so well

I may be on to something. Apparently the XT lost the 5 hp in 1996, went from 45 hp down to 40 hp. That year they changed the camshaft.
1996 on camshaft: 1jk-12170-00
1986-2005 camshaft: 1JK-12171-00-00


I already have tried opening up the intake/exhaust with no noticeable change in power. Jens Eskilden has done lots of modifications to his bike without any big change in power.

A bike that is heavily restricted on the intake and exhaust should respond more to uncorking, so the bottleneck must be somewhere else.


1. First the basic question, has anyone compared the pre- and post 1995 XT600E? Is the power difference real?
2. Does anyone have access to pre and post XT600E/XT600 camshafts? Is there a difference in lift or grind?

Thanks Mezo great info. The numbers are not the same though, if you take a closer look. Unless I am misunderstanding something:confused1:

1996 on camshaft: 1jk-12170-00
1986-2005 camshaft: 1JK-12171-00-00

(You're not misunderstanding anything).

Sounds like you -are- onto something, G600 - it could well be a differently-profiled cam.

It may be that Yamaha tried to flatten the torque curve a bit, to make the torque even more usable, in which case the slightly-softened BHP would actually be a good thing (unless you have a racing XT!)... But then again, the cynic in me wonders whether it was more to do with reducing noise and keeping emissions in check :rain:. Maybe it was to address both angles.

Thanks Mezo. So this is not it.

Back to basics. Has anyone ridden the older and newer (pre-and post 1996) XT600E back to back? Are the older bikes more powerful?

Did anyone find out whats the difference on these engines, where did the 5hp go?

I would also like to know where the power went!!

Has anyone actually tested the 2 models to compare, on ie a dyno?
How does the stated Hp compare to what's written in yamahas own factory workshop manual (with all the specs)

Just so we know we arent chasing ghosts. I've seen HP-figures go up and down on many bikes, with the same engine. Some 2-stroke ktm bikes is even listed at under 50% of actual Hp

The 3tb I had was no faster than the 4pt :)

Due to more stringent emissions requirements, the power of the XT 600 E, which had become the only available model, was reduced by 4 kW to 29 kW (39 hp), and a tachometer was reintegrated in the cockpit. The clutch actuation on the engine body was moved from the left to the right side, and the muffler was no longer part of the rear frame.
MY 99-03 DJ02 XT 600 E 25 to 29 kW (34–39 hp)
XT 600 E 1999,00,01,02 DJ021 EUR

I dont know, all the other info is correct so why would they lie about the hp? I will try to compare them in a couple of weeks. But then with mine that have kn, new exhaust all the way and dynojet kit, the other only have changed muffler.