They visually look the same so you'll have to check the angle between lob centres to a known Mk 2 profile.
ET: Engine (Twin) Robinson 105 cams or mk3's for my fast touring shadow.. ?
- Thread starter nickthehod
- Start date
Thanks ... Oh dear
You need a square Somerton cam to go with those followers, I have had them in my Special since 1980 Cheers Bill.
Would you share you cam timing with us on the Robinson Mk2 cams?I put a pair of Robinson 105 cams into my racing sidecar engine that ran on methanol. We found the engine produced excellent bottom end power but hit a brick wall at 5,000 rpm. After many months of fiddling with everything including the length of the inlet manifolds I ran it on an inertia dynamometer without air filters (large K&N) and found all of the mixture was being blown out the carbs like a fire extinguisher going off. It simply wouldn't rev above 5,500 rpm even with no dyno load on the engine! I knew the inlet had retarded inlet (opening late) but I couldn't advance it without the exhaust opening too early. Switched over to Robinson Mk2 cams and problem solved with no other changes made. Lots of revs and rear wheel 70 hp then the crankpin broke next meeting. This finding was reflected in my earlier comments about needing to advance the inlet cam as much as possible to get power at higher engine speeds. I know others have an opposite view so each to our own.
Gary Robinson makes very good cams so you're in good hands. Personally I'd stick to Mk 1 cams for a road bike just for that bottom end power (now that's going to get the fur flying!).
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Robinson Mk IIs time up with the same timing and lift as original Mk IIs. I have done lift profiles of some and could post a diagram next week if required but I'm pretty sure it is in here somewhere and also in MPH several years ago.
I have a brand new Gary Robinson Mk2, Ready for my New Comet, I could post a photo, But I don't think you could see the change from 105. Cheers Bill.
I suppose in the absence of a spare unfilled timing chest you could stick a cam (with or without wheel) on a loose spindle in a vice with a dial gauge and an attached timing disk and chart the two lift curves for one cam revolution on a chart then repeat for each cam that would at least differentiate them but could you then identify which was which from the charts?
I needed to look at my notes again. Here is what I use to check my work, so I hope it is accurate:
I would just reiterate that the 105 number is where max intake lift occurs on the degree wheel and is not the LSA. I think the LSA on almost all these cams is around 97 degrees, but that is measured at .050" and you will get slightly different numbers at the many different non-standard heights that Vincent owners use. I am not certain, but Terry's MK2 may have a higher LSA.
Unfortunately, I dismantled my cam tester when Pat Manning needed a set of crank cases. He promised to give me another set, but I am still waiting!
David
Thanks everyone but are we drifting off topic a bit? I know there is an awful lot of chat already on here about timing up the cams Please tell me more about the Pro's and cons of 105 versus Mk 3's
Keep up the good work!!
Keep up the good work!!
The Mk3 is supposed to be a Mk1 with quieting ramps, although nobody has tracked the ramps down. I would go with the Mk3. It is a good cam and was designed for the Vincent twin. Both Phil Irving and Phil Vincent did not want to supply the Mk 2 for street bikes because of the need for special fitting and the poor starting, although many have lived pretty easily with these foibles. I would vote for the stock cams for stock use.
As for the timing of the Hamilton 105, Bryan Hill published this in MPH:
David
As for the timing of the Hamilton 105, Bryan Hill published this in MPH:
David