K100 advance intake cam - K-Bikes.com - Excellence in Motion
 
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post #1 of 7 (permalink) Old Feb 1st, 2016, 10:18 pm Thread Starter
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K100 advance intake cam

Has anyone advanced the intake cam one tooth on an '85 K100? I'm concerned about piston/valve clearance.
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post #2 of 7 (permalink) Old Feb 2nd, 2016, 8:41 am
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Each tooth on the cam sprocket changes the cam timing by 10.6 degrees. You must also consider valve to valve clearance. I expended a lot of energy playing with the cam timing years ago. You can move the torque peak around maybe 500 rpm, higher or lower, depending on which way you go with the timing. I was adjusting both cams, initially to get more top end power and living with a flat spot down low (3000-4000). I got tired of that and set them for more low end. I forget exactly which way I was going.

It seems to me that if you consider valve overlap, more overlap favors higher rpm and less favors lower rpm. I might be wrong about that.

What are you hoping to accomplish?

Frank

'17 R1200RS, 2 yrs. 27,000 mi.
'16 R1200RS, 18 mo. 28,000 mi. (gone)
'03 R1100S Boxer Cup Replika 6/200
'85 K100/1100RS, 34 yrs. 326,000 mi.
'05 R1200ST, 8 yrs. 57,400 mi.-3rd deer killed it.
'11 R1200RT, 2 yrs. 30,000 mi. (gone)
'99 R1100S, 2 yrs. 15,000 mi. (gone)
'96 Ducati 900SS/SP, 12 yrs. (gone)
500,000+ BMW miles
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post #3 of 7 (permalink) Old Feb 2nd, 2016, 9:14 am Thread Starter
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k100 advance intake cam

Anything you can recall about the clearances between the valves and piston would be greatly appreciated for sure. What I'm trying to do is deaden the low end power of the bike to create high rpm power hit. I'm not necessarily interested in getting more power per se. Along with any decrease in engine braking I can get by doing this. I also want to raise the rpm limit. Maybe aftermarket electronic gear. The bike is a custom and I want to create a bike that's begging to be flogged like a two stroke.
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post #4 of 7 (permalink) Old Feb 2nd, 2016, 5:32 pm
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I was playing around with that about 20 years ago. I never checked piston to valve or valve to valve clearances. I was also staying within 8-10 deg. +/-. Be VERY careful with this. 10.6 degrees at the cam sprocket is 21.2 degrees at the crank!

If you are looking for more power- I'd suggest transplanting a later K1100/1200 16 valve. That's what I did and the K100 8 valve can't compare, even in modified form (except turbocharging). I bought a K1100 engine, Motronic and wiring, airbox, etc. for reasonable money out of a salvage yard. A 1200 will fit with the old style bellhousing. 1100 is a straight bolt up. The problem is altering the '85 wiring harness to run the later Motronic system. Not for the faint of heart!

I see you are in Austin.

Frank

'17 R1200RS, 2 yrs. 27,000 mi.
'16 R1200RS, 18 mo. 28,000 mi. (gone)
'03 R1100S Boxer Cup Replika 6/200
'85 K100/1100RS, 34 yrs. 326,000 mi.
'05 R1200ST, 8 yrs. 57,400 mi.-3rd deer killed it.
'11 R1200RT, 2 yrs. 30,000 mi. (gone)
'99 R1100S, 2 yrs. 15,000 mi. (gone)
'96 Ducati 900SS/SP, 12 yrs. (gone)
500,000+ BMW miles
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post #5 of 7 (permalink) Old Feb 2nd, 2016, 5:38 pm
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I re-read your last entry. My only experience with super revving the K100 was with a friend in the late 80's who had modded to rev to 10,000 (Luftmeister at that time). He spun several rod bearings pretty quickly. The design of these engines aren't really suited that.

Frank

'17 R1200RS, 2 yrs. 27,000 mi.
'16 R1200RS, 18 mo. 28,000 mi. (gone)
'03 R1100S Boxer Cup Replika 6/200
'85 K100/1100RS, 34 yrs. 326,000 mi.
'05 R1200ST, 8 yrs. 57,400 mi.-3rd deer killed it.
'11 R1200RT, 2 yrs. 30,000 mi. (gone)
'99 R1100S, 2 yrs. 15,000 mi. (gone)
'96 Ducati 900SS/SP, 12 yrs. (gone)
500,000+ BMW miles
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post #6 of 7 (permalink) Old Feb 2nd, 2016, 7:03 pm Thread Starter
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Maybe I'll just let it shut off at 9k. The bike has such great power at 3k that you tend to ride it right there. So I want to get rid of that. Carefully.
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post #7 of 7 (permalink) Old Apr 29th, 2016, 9:32 pm
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You can make incremental changes in timing by grinding away a potion of the indexing pin on the cam sprocket(s). You might want to replace your cams to 49-state cams instead of the 50-state version. The part numbers are: 11 31 1 460 045 for the intake, and 11 31 1 460 044 for exhaust. They have more duration and pull harder on top. If you want to spin the motor much higher than stock, consider a later-model oil/water pump. By lowering the internal gearing of the pump, cavitation of the pump was moved to a higher RPM. This pump is found on most '90 and later Ks.
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