Suzuki Burgman modification (aerodynamics + gearing mods)

[janvos39]

Hi Craig
I made a new set of gears in the gearbox. All straight gears.
The standard gearbox consists in following gears with number of teeth.
Ingoing shaft to intermediate shaft 14 at 31 teeth
From intermediate shaft to outgoingwheel shaft 14 at 39 teeth
So total this gives a reduction ratio of 6.168
I changed this ratio and also added an additional ratio so to say a second gear which I shift with the lever on the handle bar.
Ratio of my first gear is 5.896
Ratio of my second gear is 4.803
Follow the pictures to see the hardware. regards

Jan

[dcb]

I'm still little lost how you are shifting too, course I don't own a burgman to have any point of reference either, but did see some pics on pages 63, 64 (and 32 to get my bearings) in this manual.

Suzuki Burgman AN400 2003

Guessing that you brought the idler shaft end out so you could twist or push on it, but no shot of the internal gears to make sense out of it.

[janvos39]

Dcb the idler shaft is pictured on page two. The two seprated gears go on this shaft. The hole assembly is in the second picture of this page. The internal of the idler shaft is shown in the third picture. The aluminum bloc is on the wheelside (your page 62). As can be seen on page 7. Here also is shown how the shifting is transformend in a rotation. This partly rotating shaft is coupled to a cable which leads to the handlebar.
I will also give soon the drawing cross section of this gearbox to make things clear.
jan

[dcb]

The picture on page 2 helps a lot, thx, and very nice BTW

[janvos39]

I had a problem with the overdrive in my gearbox. The shifting pin broke when shifting down. Since this shifting has to happen without the help of a clutch it is a very delicate moment. Normally i drop the speed to 25 mph before shifting down from the overdrive gear to the first gear. Only once I did this at a higher speed with the broken pin as result. So I had to go back to the standard Suzuki gearbox. And immedately the MPG dropped.
The plan is now to work with a stronger shifting pin including a support ring and to add an overrunning clutch in the wheel drive shaft. So shifting down will be done without the bike driving the gearbox.
This will also allow me to run idle when throttle is closed and do some coasting or when I have a larger battery installed do EOC.

[janvos39]

After reinstalling the repaired gearbox I have the FE up to 75MPG
In the gearbox I changed the ratios slightly. First gear is now identical to standard Burgman (18.3 km per 1000 rpm). Second gear is now 25 km per 1000 rpm. And ofcourse if you followed the previous posts the overrunning clutch is in.



Above the first tanks after the rebuild. This is still without any hypermiling.
One of the things to do next is a gasoline measurement system on the carburettor. I have ordered a small Swiss flowmeter. The electronics is worked on to give a readout on a display during riding.This step is needed to see the effect of small changings to the aerodynamics of the bike as well as to find out what the best gearshift speed is based on FE.

[janvos39]

The flowmeter for measuring the fuel flow has arrived and is in the picture below. Two connections of 1/8 G and tubular ends are made to accommodate the meter inbetween the fuel pump and the carburettor.

The read out box is attached to the steering bar. A value of the fuel flow is given each second. Also the flow measurement can be accumulated over a periode that can be started and stopped by push buttons.


The system is working but not ideal yet.Very low flows are not detected. So something has to be improved to catch that also.

Parallel to improve the flow meter I am preparing the next step which is engine size reduction. The bore will be reduced from 83 to 73 mm with the same stroke. So the engine capacity drops from 385 to 297 cc. This should reduce the fuel consumption due to lower idle use and a better BSFC at the higher mean pressure .

The picture shows the piston and cylinder of the 73 and 83 mm size.
The bolt pattern is identical.

There is a difference in weight for the piston and pin combination. This is 64 grams. I will add this weight to the pin of the 73 mm bore to keep the balancing identical.

The bore to stroke ratio becomes almost 1. Earlier in this thread we discussed the optimum value of the bore-stroke ratio for best FE.
I found a nice article on this subject from the university of Michigan.

http://journals.pepublishing.com/con...471201u6u5q51/

It looks like around 4000 rpm the bore equal to the stroke is not bad.

Below the latest results on FE with the modifications sofar on the Burgman scoot.

[The Atomic Ass]

Amazing. I wish I had your technical expertise, as well as workshop.

[Frank]

Great work!

[janvos39]

To check how much power I loose when going to 297 instead of the 385 cc I flowed the heads of the 250 and the 385. The under pressure used for themeasurement is 18 inch of water. As can be seen on the graph the 250 is about 10 grams less than the 385 so I estimate that this will cost me 6 to 7 horsepower. Maybe this can be limited to less if I can find some grams of air in the 250 head by some reshaping of the inlet track.



Below the head of the 250 on the flowbench.



The camshaft of the 250 and 385 have an identical profile given in the drawing below.