Extra cubes?

[a1bummer]

Where do the MKII's get the extra cubes compared to the MKI's? It it a larger bore? Longer stroke? Or both?

[a1bummer]

After a bit of research this morning, the 1300ccm engine would have a bigger bore. Both engines have the same part numbers for the crank and con rods. The 1200ccm bore and stroke is 7.6cm & 6.6cm. I don't have the specs in front of me anywhere, so I'm assuming the bore on the 1300's is about 7.92cm?

[GaryZ]

Here is a comparo chart that I put together from online service manuals;

[Big Daddy]

The real question is why are the MkI bikes so much faster with less cubes?

[frankd]

The real question is why are the MkI bikes so much faster with less cubes?

 

Well, the MkII's weigh about 50# more. Also, it feels like they have milder cams, but that may be due to the larger motor (larger motors make identical camshafts feel milder). I've got to solve the clutch slipping problem in my old 1200 (now my brother's) so I can see how much faster they are. In addition to the bike's 50#, I weigh about 50# more than my brother.

 

Frank D.

[Condor]

Here is a comparo chart that I put together from online service manuals;

 

I noticed that the HP rating for the 1200 and 1300 is the same at 97hp. I thought the 1200's were rated a little less at around 94, but I just scanned thru an '83 1200 service manual and it doesn't mention any hp rating. Where did you find the ratings??

 

BTW... nice chart. I have it copied.

[Squeeze]

Here is a comparo chart that I put together from online service manuals;

 

With a quick browsing i see you Chart is wrong at the front Brake Diameters.

 

MKI is 267mm, MKII is 282mm, VMax is 282mm until 1993 and 298mm afterwards

[Condor]

With a quick browsing i see you Chart is wrong at the front Brake Diameters.

 

MKI is 267mm, MKII is 282mm, VMax is 282mm until 1993 and 298mm afterwards

 

Also noticed the years posted at the top of the column are a bit off. 1200=1983-85, 1300=1986-93, Vmax is OK, RSV=1999-present

[a1bummer]

With a quick browsing i see you Chart is wrong at the front Brake Diameters.

 

MKI is 267mm, MKII is 282mm, VMax is 282mm until 1993 and 298mm afterwards

 

Ummm... in my manual it says 298.00x8.5mm for the MKI. Same as the chart. I would have to believe what it states since I couldn't fit the rotor covers off a MKII onto my MKI. They were to small.

 

THANKS FOR THE CHART!

[Squeeze]

Ummm... in my manual it says 298.00x8.5mm for the MKI. Same as the chart. I would have to believe what it states since I couldn't fit the rotor covers off a MKII onto my MKI. They were to small.

 

THANKS FOR THE CHART!

 

Well, that's very interesting Info right there... I'm very sorry to hear that i provide false Information. Please accept my Apologies. I allways was in believe the MKI Rotors being 267mm Diameter.

 

If these are 298mm, i might have a new and very fine Solution for upgrading the Brakes on the MK I.

 

Could somebody provide Measurements and Pics from the Rotors and the Brake Calipers of a MK I ?? Pics should be taken from a nearly exact right Angle and of Course, without any Covers. I need a clear View to the Rotor Diameter and the Caliper Mounting Bolts in Relation to the Fork Leg.

[GaryZ]

Thanks for the comments on the chart. I updated the top of the chart to reflect the years of production. However, some of the data may have changed during those production years. Most of the info comes out of the free service manuals available on this forum. The HP and torque figures are from research of magazine reviews online.

 

Yes, the MKI is listed as having 298 mm front rotors in the "8385servicemanual.pdf"

 

I would tend to agree that the MKI is probably faster in stock form due to the weight difference.

 

Notice the listed cylinder pressure. This suggests to me that the 2nd Gen has very different cams vs the MKI and MKII.

[pegscraper]

The real question is why are the MkI bikes so much faster with less cubes?

 

The biggest reason if not the only reason, is that the MkI is geared lower. To my knowledge, per the part numbers, the cams are all the same thing. "Feel" and "cylinder pressure" are not good indicators of cam specs.

[GaryZ]

Here are a couple of pictures showing the general size of my 1985 VR front discs;

Looks like 298 mm is correct for my bike.

[Big Daddy]

Wow! You really smart guys know how to take the fun out of being a troublemaker!

[Squeeze]

Here are a couple of pictures showing the general size of my 1985 VR front discs;

Looks like 298 mm is correct for my bike.

 

Thank you for the Pics. Now, I have something to think about regarding contemporary Brakes ...

[Condor]

Thank you for the Pics. Now, I have something to think about regarding contemporary Brakes ...

 

The only difference I can see is that the MK2 rotors are slotted, and the MK1's are solid. Next week Kurt (gone14s) is going to swap out the front forks on the '83 for a set of MK2's for me. I'll probably swap out the rotors too. I do like those slots....

[TIMEtoRIDE]

The hot set-up for brakes is diagonally milled grooves, that don't go all the way thru like slots do. They vent brake pressure, increase surface area, scrape the pads, and don't decrease strength (much).

[Yammer Dan]

So if I cut grooves in that cinder block I have tied to the end of the rope I can stop quicker???

[Condor]

So if I cut grooves in that cinder block I have tied to the end of the rope I can stop quicker???

 

 

Groan.........!!!!!!

[Guest HdHtr]

So if I cut grooves in that cinder block I have tied to the end of the rope I can stop quicker???

Probably not Dan, maybe you should try two blocks or thicker soles on your boots? I think Dr Sholls makes a heat proof insert to keep your feet cooler ...