The 50

**cotswold** · 11th May 2014, 19:35

I popped the KTM piston on today and measured the port timing of the worked up cylinder to see where they are at. With the spacer removed I still have a negative deck height but not too bad. The exhaust port is at 196* and the transfer is at 140* ATDC.
This is my scrap cylinder but had planned on copying the porting on my new one. not sure now.

**F5 Dave** · 12th May 2014, 10:35

Sorry you've confused the crap out of me mixing open durations & ATDC measurement.

or have you got 140 deg transfer duration. Because that is crazy. probably required for 20,000rpm.

**cotswold** · 12th May 2014, 21:40

Originally Posted by F5 Dave

Sorry you've confused the crap out of me mixing open durations & ATDC measurement.

or have you got 140 deg transfer duration. Because that is crazy. probably required for 20,000rpm.

I live in a confused state most of the time, with the piston at TDC the ex opens at 83* and the Trans Opens at 107*

Does this mean my transfers are too high.

20k is about 2k more than I want

**F5 Dave** · 13th May 2014, 02:07

Which means 24* blowdown. No where near enough. Too high.

**cotswold** · 24th May 2014, 17:48

Just a quick progression report.
As I cant just bolt an MX85 into my RS chassis I thought I'd do some more work to the 50, this one is too big to be legal but may as well make 2 motors and use this one in B grade. I'll get one of the oversize KTM 50 pistons so I can interchange bottom ends with out issue.

Thanks to Malcolm and F5 Dave I have these head bearings for the RS chassis.

**cotswold** · 1st June 2014, 15:28

I had an hour to myself today and a bit of scrap ally on my garage floor so made up a bell mouth for the 28mm PWK off the 50. Is there any need for one and would there be a size I should have been aiming for?

**kel** · 1st June 2014, 18:59

Originally Posted by cotswold

Is there any need for one and would there be a size I should have been aiming for?

Absolutely but you want to keep the carb length short as possible

Click image for larger version.

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have a read of this

**cotswold** · 18th June 2014, 14:34

I would like to try triple porting my NSR cylinder but on inspection mr. Honda has not left me any metal either side of the exhaust port exit to allow this. Question can I have the water gallery built up so I can put 2 extra ports in or is it in the too hard basket.

**Farmaken** · 18th June 2014, 16:19

Cast Iron arc welding electrodes should do the job - maybe some devcon over the top to make sure it's water tight.
Extremely good chance of the bore distorting to some degree unfortunately

Thanks again for the help on the weekend, spent another half hour getting that tyre to seal and inflate

**Henk** · 18th June 2014, 17:32

Originally Posted by Farmaken

Cast Iron arc welding electrodes should do the job - maybe some devcon over the top to make sure it's water tight.
Extremely good chance of the bore distorting to some degree unfortunately

Thanks again for the help on the weekend, spent another half hour getting that tyre to seal and inflate

Do you ever have any GOOD luck?
Was bloody good to see you again, shame you had so many issues when you got here.

**mr bucketracer** · 18th June 2014, 18:01

Originally Posted by Henk

Do you ever have any GOOD luck?
Was bloody good to see you again, shame you had so many issues when you got here.

time for a 4 stroker for ken i think (-; , missing having some good racing with him

**F5 Dave** · 18th June 2014, 22:30

My RG was the same. Too hard for me.

**cotswold** · 14th July 2014, 15:53

Help ! I just dropped off my NSR 50 cylinder and the KTM 50 piston and they want to know what clearance I require, does anyone have an idea?

**husaberg** · 14th July 2014, 15:56

Originally Posted by cotswold

Help ! I just dropped off my NSR 50 cylinder and the KTM 50 piston and they want to know what clearance I require, does anyone have an idea?

Fits posted a rule of thumb on ese re clearances so much per mm bore but how it applies with a cylinder with a sleeve vs a piston for a coated cylinder i have no idea.............