TTR(ammelbak) Tuning to 41bhp, 48Nm @ rear wheel

[Rammelbak]

I'm sorry to do this in English. My German is not good enough to describe everything properly. Hopefully everybody can read and understand the message.

Main goal: lower the engine oil temperature without using extra oil cooler. I believe that an oil cooler is fighting the symptoms instead of curing the disease. In the past I have ported a Moto Guzzi V50. The main goal was achieved. As a "bonus", the bike also got extra torque and power. Now I did the same with the TTR. To get to that result, I concentrate mainly on the exhaust gases. The idea it to get the hot gasses out of the engine as soon as possible to prevent them from heating up the cylinder head.

The engine: the bottom end of the engine is original TTR engine with 65.000km on the clock. The complete top end (cylinder, piston, cylinder head) is from a XT600 2KF from 1989 with 40.000km on the clock. The camshaft is standard, the CDI is standard, the compression is lowered, the carburetor is standard.

The modifications

Inlet:

• inlet valves from a Ducati 916 because of their slimmer profile
• replace air filter for a single layer TwinAir foam filter
• removed the snorkel from the air box
• enlarged the intake hole in the air box to maximum

Combustion chamber:

• removed all the high material between the valves
• removed material around the sunken exhaust valves (this is only in the 2KF-cylinder head, not in an original TTR cylinder head)
• removed squish edge around the exhaust valves

Exhaust:

• exhaust valves from Hyundai, 6mm valve stern (with 6mm valve stern guides from BMW), 25 degree back-cut on the valve dish
• exhaust valve seat inside material removed (see image) to 29.6mm diameter (OEM: 26,9mm diameter)
• removed material from exhaust port over the full length to 35mm diameter at the end (OEM: 30mm diameter)
• custom build exhaust system. Exhaust header made from stainless tube 38x1,5mm (OEM: 31x1,5mm) and link pipe from stainless tube 51x1,5mm (OEM: 41x1,5mm)
• exhaust silencer from Yamaha R1 2002 with the catalytic converter removed

The carburetor is tuned on a dyno meter. The results are 41bhp @ 6900rpm and 48Nm @ 5300rpm at the rear wheel

On this website there is a power diagram from a original TTR (with the CDI wire disconnected). That one has 35 bph and 42Nm (4.3kgm x 9,81). That is an increase of 6 bhp (17%) and 6 Nm (14%)




Unfortunately I did not measure the performance before the modification. To compare the results, I took the diagram from this website about the CDI disconnected wire. To compare, I have plotted the blue line on that diagram, and the results from my bike in a Excel diagram. Off course this is NOT a perfect comparison. Somehow on the original diagram the engine runs a maximum 7200rpm. On the dynometer my engine runs a maximum of 78000rpm. If I shift my diagram to a maximum of 7200rpm and put it in the same diagram as the original, this is the result:




Off course there is more power to win with a special cam shaft and Mikuni flat slide carburetors, but that stuff is expensive! The modifications that I made are reasonably affordable. Most of the stuff I could do myself in my garage with a welding machine and a good quality Dremel.

The main goal: lower the oil temperature! During the dyno testing the oil temperature did not go over 80 degree Celcius. Next summer on during offroad driving it will become clear if the engine really stays cool under every condition.

Extra goal: the Yamaha R1 exhaust silencer is extremely quiet!!!

[becki]

Hey Rammelbak,
Thx for sharing this information.
what have you to do to get the 6mm valve guides from BMW and the valves in the XT Head, any maching ?

[Rammelbak]

The guides and the valve seats are modified at a engine machine shop. Replacing the valve guides is a specialist job that I can not do. The valve seats are to hard to modify with a Dremel. I think that it is important that the combination of the shape of the valve and the valve seat are exactly like the drawing. Just making the ports bigger without modifying the valve seat and valve, will not give the same results.

Specialist job: making the valve seats wider like the drawing. When you go to a engine machine shop they will advise you NOT to modify the valve seats this way because they think it will have a bad effect. In reality it works positive



The valves of the Hyundai and the Ducati need to be made shorter. This is an easy and cheap job for a engine machine shop. Extra bonus: the Hyundai valves are only €11,= a piece

I think it is not absolutely necessary to replace the valves. If you can grind the original valves to the same shape as the Hyundai and Ducati valve, that would probably also work.

Today I took the TTR for the first test drive on the road. It feels STRONG!!

[Torn]

Nice work. I can recommend to use weaker valve springs, probably in combination with titanium tops. In the valve train is much potential to free some extra horses. Many years ago I got a special designed camshaft from a german guy who was working at an university and I got a cam with slightly more stroke and opening time with lower valve accelaration. So with his given values and some other modifications it was possible to give about 6-10kg per spring free with stock valve on an 34K head which has the slightly smaller valves (which I prefer because they give with used YDIS the better turbulence on filling the combustion chamber). Even the stock cam can be fitted with weaker springs.

For grinding the intake I better took a Bosch GGS heavy series than a Dremel - you can easily grind even the inner diameter of the valve seats with them.
Next hint: opening full the air flow hole between both intake ports - often its really bad closed because of bad cast cores. I always opened them from 3-4mm to about 11mm in diameter. The airflow from frontal around the sparkplug will be optimized to the back.

[Rammelbak]

Hi Torn,

Can you tell a bit more about your modifications? What would be the main goal of having weaker springs?

The camshaft sounds interesting. Do you have a camshaft timing diagram of that? Of something to show the shape of the cams?

I did not know the Bosch GGS series. They are some serious equipment I call it a "dremel" because everybody understands that. In my garage I use something like this: https://www.hbm-machines.com/producten/ ... or-model-1

The main goal of my experiment was lowering the oil temperature. To achieve this, I concentrated on the exhaust ports for the simple reason: what goes in must come out. The easier the hot exhaust gasses can get out of the cylinder head, the less heat they will transfer to the cylinder head. That is why I start at the valve seat. I don't know if I could work on the valve seat that precise with the Bosch GGS. Could you grind the seat exactly to the shape of the drawing with that machine?

Now that the exhaust is optimal, I could concentrate on the inlet. But I do not exactly understand what you did with the inlet. Can you show in a drawing what part of the inlet ports you grind material away?

I'm really curious to the end result of your tuning. Do you have a dyna diagram?

[Torn]

The weaker springs are only fitted because in stock engines they use in safety issues very strong ones. But so you loose a lot of power in compressing the spring - each round the crankshaft needs to compress 2 springs. So if you optimize the weigth of the whole valve train to your spring rate you can free a lot of power. So in combination with titanium toppers you will get rid of some more gramms which even needs weaker springs. So I prefer better the old heads (you can fit them on new cylinders, too, if you modify them a bit) because of the smaller valves. They are lighter and you have more space to the cylinder wall which optimizes the flow in.
I think my main modifications have been the same you did on your ports - so I have no picture from this. On a 2KF head I even tried out to give the left intake port a natural curved flow - that was good for optimizing the torque in lower rpm.

I use this GGS27 at home:

GGS27.jpg

but with these grinding heads:

Fräser.jpg

there are sevarel different machines available but this I know from my work for pipe systems and we used them for preparing the welding areas. It is like all machines a bit training necessary but if you have, you can do really nice stuff. Your flexible Dremel might be good, too - we have had those at work, but the real strong ones are extremly expensive - the flexible shaft was even over 300€ I remember.

In my time of modding engines I just tried out and never got to a dyna - but if a 3TB can go on back wheel in 3rd gear without any clutch play I guess the aim was achieved