Connecting rods

splatt · Jun 19, 2009

what locates the cap to the rod,is it doweled or does it just rely on the bolts,you should check to see that your socket isn't pushing the cap over as you do the bolts up.If the cap is moving it is a shit design and will need a good firm rap with a plastic hammer on the side of the cap to centralise it,

Foxy · Jun 19, 2009

Hi all, geez this post has got me thinking hard as Ive purchased those good lookin & pretty exspensive MAP rods for my 920 90 deg offset crank Commando motor. Im hoping the larger bore solves any of the case clearance problems and Geoff Collins supplies fitted big end shell bearings to suit crank and rod type, so hopefully theres no dramatic changes to my plans. The MAP rods have beautifully CNC machined groves to lock the rod caps in place so if they move there, shits gonna happen big time! I agree the obvious way to check clearance would be without the pistons fitted in the barrels.

regards Foxy

chris plant · Jun 19, 2009

hi foxy, without the pistons fitted you,re only going to see how much side clearance there is,you wont see how much there is behind the rod(ie nearest the cylinder wall) i assume you got your offset flywheel from geof collins,did he modify your cam too

grandpaul · Jun 19, 2009

Righty-O

Without the pistons in place, excessive rod range-of-motion will be allowed, and may indeed interfere with cylinder skirt; whereas with piston in place, the range of motion fore-aft is limited to the rod small end traveling only up the dead center of the bore.

If you don't do the checking with the pistons in place, you'll be doing unneccessary work to clearance the cylinder skirts, removing material that is beneficial to have in place.

splatt · Jun 19, 2009

with the piston in place you arent going to see any thing,do the map rod have V GROOVES on the face or is it just a straight step?

grandpaul · Jun 19, 2009

As mentioned in one of my previous posts, you certinaly can see the skirt to rod clearance by simply raising the cylinders.

The better method mentioned was to use only one case half, tightening the cylinder in place for full effect of minimalizing the clearance at the point in question.

The piston really does have to be in place for the measurement to mean anything.

JimC · Jun 19, 2009

It's not the piston skirt to rod clearance that's in question. It's the cylinder skirt to rod clearance that is the issue. If I'm correct, it's the width of the cross section of the MAP rods that is of concern.

splatt · Jun 19, 2009

grandpaul said:
The piston really does have to be in place for the measurement to mean anything.

Why ,surely a chimpanzee could hold the pin end in the middle of the cylinder as he winds it over, or why not get him to measure how much wider and bigger the new rods are and enlarge as required? although they don't sound like good rods any way, just out of curiuosity ,what is a CARRILLO rod worth in US$?

Hortons Norton · Jun 19, 2009

For Jim's pair they go between 6 and 7 hundred but those are custom made.

Hortons Norton · Jun 19, 2009

Anyone know how much for a standard pair?

splatt · Jun 19, 2009

my , they have gotten quite spendy in the last 20 years, I brought a set for my trident in 88 and I think they were about $175 US then

grandpaul · Jun 19, 2009

Sure, anyone can hold a .060 tolerance with their fingers in between cylinders and block as they rotate the crank!

Yeah, why not use that method...

it costs nothing to install the piston, and results in an accurate measurement.

bpatton · Jun 19, 2009

splatt said:
what locates the cap to the rod,is it doweled or does it just rely on the bolts,you should check to see that your socket isn't pushing the cap over as you do the bolts up.If the cap is moving it is a shit design and will need a good firm rap with a plastic hammer on the side of the cap to centralise it,

I've heard of a method where one uses feeler gauges on either side of the rod when it's being tightened on the crank. Looking down on the cap, you would put the blades downward so they contact both the cap and the rod proper on both sides. The idea is to keep them from shifting or twisting on each other while you torque it down. It conveniently lets you know what the side play of your rods are at the same time too.

Foxy · Jun 20, 2009

Gday Chris, yep Geoff Collins of ED G offset cranks supplies a 90 degree Newman made Camshaft to suit. I believe its a slightly hotter Combat cam with a higher lift and longer duration.
Below hopfully will be a photo of a MAP rod showing the machining of its cap to lock it in place when installed. You will also see that it hasnt got the oil hole drilling for the cylinder lubrication as original rods have. Im tempted to drill it as Im hoping to install a CNW style crank vent to free up the bottom end and help expel the oil there. But Im wondering in doing so reduces cylinder wall lubrication too much if theres no lube coming from the rods? Any thoughts?

FOXY

bpatton · Jun 20, 2009

Foxy said:
Gday Chris, yep Geoff Collins of ED G offset cranks supplies a 90 degree Newman made Camshaft to suit. I believe its a slightly hotter Combat cam with a higher lift and longer duration.
Below hopfully will be a photo of a MAP rod showing the machining of its cap to lock it in place when installed. You will also see that it hasnt got the oil hole drilling for the cylinder lubrication as original rods have. Im tempted to drill it as Im hoping to install a CNW style crank vent to free up the bottom end and help expel the oil there. But Im wondering in doing so reduces cylinder wall lubrication too much if theres no lube coming from the rods? Any thoughts?

Foxy

I've been told that the oil hole in the rod was put there to oil the wristpin and cool the piston as much as anything else. A few well known Norton builders reverse the shells to intentionally cover them. The way that plain bearings work is that they are a controlled leak. They require flow for cooling and the outlet is around the sides of the rod. It gets everyplace. It's an "oil storm" in there anyway.
Sportbike by Kevin Cameron gives a nice explaination of how plain bearings work.

JimC · Jun 21, 2009

Aren't the Carrillo rods without the oil hole?

bpatton · Jun 21, 2009

JimC said:
Aren't the Carrillo rods without the oil hole?

Yes you're right, doesn't seem to be a way to have one with an H beam rod. (I'm editing from here on out.) I looked a Carrillo rod and there's no reason that they couldn't put in oiling holes at the big end because there are holes in the small end, for the wristpin. But in this case they chose not to.

Foxy · Jun 22, 2009

Many thanks bpatton for your reply and informative explanation. Ive taken it on board and also checked out Kevin Camerons article
regards FOXY

bigstu · Jun 26, 2009

Re: brakes

Hi JimC
Finally got the 11mm master cylinder bled with the help of another set of hands. Also used a braided hose.
Tested last night. You can pull the lever almost back to the bars at standstill if you try, just like a modern system.
On the road you need one finger to pull the bike up.
Now I need a fork brace!
Thanks Jim, if it wasn't for your advice I would have gone for 13 of 14mm piston diameter as per RGM advice.
Stu.

Connecting rods

Similar threads