engine tuning

[perok]

I have just ordered new main jets (132,5) from Mikuni Topham. I have already modified the air intake. I made a bigger inlet hole in the airbox. Also modified the standard exhaust.
When I will change the main jets is it necessary to change the needle jet position? What is the correct postion of a needle for bigger jets?
I would also like to know what are the restrictors on the throotle slides in the carburetor which I have to remove, as I read in some coments on the forum. (Some photo will be welcome)

Thank you for your help in advance!

[riedrider]

Hello Peter,
if you scroll down to the bottom of the page you will find a picture of the carburettor cover with the restrictor removed. On bottom left is the original restrictor which is clipsed to the cover from factory. The small part on the right is often installed instead:
viewtopic.php?t=13441&start=30
If you go back to page 2 of this thread you will find 3 pictures of the position of the throttle slide.
First one shows the fully opened position with stock restrictor. The second one without restrictor and the third one with this small restrictor.
You can see that without restrictor the throttle slide will move up a little bit too much so that the air flow might be disturbed a little bit.
The small restrictor shall prevent this.

[perok]

Thank you riedrider. I understand now what I have to do.

What about the needle position. Do I have to change it for bigger jets or leave it as it is?

[sandro]

Hello Peter,
TOPHAM still offers a complete tuning kit for the Bulldog.
http://www.mikuni-topham.de/ENGLISHSITE ... glish.html (search "YAMAHA" left)
In the installation instructions, there is no notice about changing the needle position,
just like in the instructions of kits from other dealers like KRAUSE.
So I think, most of us didn't change it.