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850 T-3 mid range boost?

fouled plug

Just got it firing!
Joined
Feb 20, 2009
Messages
2
Hi All,

Looking for comments on the following approach I want to take w/ a stock t-3 motor...

I am looking to boost mid-range grunt w/ a t-3 cafe project. I'd like to install a B10 cam, remove the base gasket and install a thinner head gasket to increase compression. Cant afford timing gears now. I'd like to keep the stock carbs and ignition. I'll use the stock head pipes, crossover and put Lafranconis on.

Question: do I have enough piston to valve clearance doing this?
Is the Dyna III ignition worth the money from a performance standpoint?

Thanks for any opinions-
 
My two cents worth,

Sorry but the very best thing you can do for performance is to fit some 36mm carbs. The big impediment to power with this engine is the short turn radius on the intake tract. I did some back to back comparison on the flow bench and a modified small valve actually flows better than the midvalve engine which makes its power from increased compression and bigger carbs.

The second best thing is to lighten the flywheel as much as possible.

The third best thing is to fit lighter throttle springs!

Increasing the compression is good - increasing the squish so you have about 40thou clearance will help greatly with keeping the engine from detonating.

There are better aftermarket cams then the B10 - like the megacycle. If you go beyond their street cam you will need to check PtoV and VtoV clearances with plasticene. Install new or resurfaced followers or risk catastrophe.

Timing gears really offer no performance gains and potentially a lot of problems. I don't want to start a flame war but IME the aftermarket aluminum kits either work fine for the life of the bike or dissolve and cause havoc. The reality is that there is little proven HP in them - I did run both on the dyno and saw no measureable difference. If you must run them then look at the original steel versions. The aftermarket timing chain tensioner works fine and is cheap. Better to put your money into a better (there is an alternative to the valeo - mitsubishi I think) starter motor which lets you fit a smaller battery which out to save you 20-30lbs of fat. The bosch will be getting old and have difficulty turning over a hi comp motor.

They Dyna is ok and certainly better than the crappy points which are almost impossible to adjust to get accurate timing and dwell. Fit 5 ohm coils.

Twin plugging is IME a great help but it depends on the fuel you have available and you must redo the distributor curve appropriately.
 
With a higher lift cam you run the risk to hit the inside con rod bolts when the cam flexes at high rpm, grind an angle on the heads of those bolts to get some clearance.
JR
 
I've heard the same thing regarding Carbs. Is there much that one could do to improve flow in the intake/exhaust ports?
 
Yes of course the inlet and exhaust tracts can be improved - you buy or make a flow bench and you sit down with some plasticine and a die grinder and see if you can improve it. A good three angle valve job is a good start - Rimflo valves type might also help.

However if the carb is too small then it is the equivalent of a big pipe with a cap with a pinhole in it or a resistor (there is something callled 'Lohmic' law which tries to take 'Ohms' law and apply it to flow - unfortunately it aint that simple).

Air is very tricky as what is downstream affects what is upstream and visa versa.

After you have put in your hot cam, fiddling with the flow bench (and then dyno) is what you have to do.

From experience if you don't have a flow bench you are really groping in the dark.
 
I just got my homemade flow bench up and running last night. I look forward to a lot of time playing with clay and die-grinders to try out several different styles of porting to see which makes the best power.
 
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