Connecting rods

JimC · Jun 18, 2009

Does anyone have experience with the connecting rods from MAP Cycle? broken link removed

littlefield · Jun 18, 2009

I hope you get some positve feedback as I've got a pair to install. They warn about checking for a 1/16 " minimum clearance between the rod and piston. Guess I'll use clay for that.

grandpaul · Jun 18, 2009

1/16" clearance between the rod and piston WHERE?

At the skirt? Then yes, clay or a feeler guage.

At the gudgeon pin? Feeler guage.

JimC · Jun 18, 2009

How do you check skirt to rod clearance with a feeler gauge ?

grandpaul · Jun 18, 2009

Tip the piston over and slip the sucker in there.

grandpaul · Jun 18, 2009

Fit up the rods to the crank per usual, then install pistons without rings, slide the cylinder in place, but block it up where you hgave a gap under the sleeve between the top of the crankcase throat. Carefully cycle the crank through till the rod and piston skirt clearance closes up, and observe / verify / measure at that point.

littlefield · Jun 18, 2009

grandpaul said:
Fit up the rods to the crank per usual, then install pistons without rings, slide the cylinder in place, but block it up where you hgave a gap under the sleeve between the top of the crankcase throat. Carefully cycle the crank through till the rod and piston skirt clearance closes up, and observe / verify / measure at that point.

That sounds like the best way.

JimC · Jun 18, 2009

I guess if you measure how much you blocked up the cylinder and subtract that from the total skirt to rod clearance it would work. When you move the cylinder up from the crankcase aren't you effectively shortening the bottom of the cylinder wall?

As for tipping the piston over and inserting it in the cylinder: skirt to cylinder clearance, yes; skirt to rod clearance, no.

chris plant · Jun 18, 2009

hi jim,just had a look at map website and it says to avoid catastrophic damage a cylinder skirt clearance of at least.060 may be required ,i took this to mean at the cylinder skirt where there are cutouts for the rods,no? i would assemble the crank and rods and pistons in one half of the cranckcase and fit the barells and rotate it to check clearance then repeat in the other cranckase half

Hortons Norton · Jun 18, 2009

I thought the same thing, If I was making rods I would make sure they would work for a certain application first, NO?

Seeley920 · Jun 18, 2009

Unfortunately I tried MAP rods :cry: You will need to open out the slot in the skirt of the barrel as the beams are wider that a standard Norton rod. the problem I had was that the small end was too tight....had to really heat the rod to get the gudgeon pin in. also next time the engine was apart I couldn't get the rods to turn on the crank once they were torqued past 10lbs! Put another set of rods from thunder engineering in, same shells etc, never looked back

grandpaul · Jun 18, 2009

PISTON skirt and CYLINDER skirt (liner, actually) are two TOTALLY different things.

Jim- as long as the piston remains "true" to the cylinder bore when you are measuring it, there is no difference whether the cylinder is lower or higher. However, the first statement (above) renders this point moot.

Chris, good suggestion on doing half case at a time.

Hortons Norton · Jun 18, 2009

The site says cylinder skirt. Not piston skirt.

chris plant · Jun 18, 2009

hi all, ive heard good reports on thunder engineering rods and carrilo rods (never heard of map till this thread)but at the end of the day std norton rods take a lot to improve on, they are good for most applications ,ie road and racing,

Cookie · Jun 18, 2009

For what I'm doing the standard rods are all I need but I do harbor a secret lust for Carrillo rods.

Hortons Norton · Jun 18, 2009

Don't we all?

splatt · Jun 18, 2009

Why fit the pistons, fit barrel over assembled cases and look down the 2 big holes as you try to turn it over you should be able to see clearly where the rods want to hit the barrel cut out ,dont nick or scratch your rods, pesonally for the money I would have bought carrillos

grandpaul · Jun 18, 2009

Initial post in this thread referred to "piston skirt" clearance to rod...

lynxnsu · Jun 19, 2009

i had the same problem as seeley920 If torqued up these big-ends distord and will not move They are nice to look at but I wouldn,t use them in an engine.btw the new conrods by Norton seem to be of inferior quality as they used to be as well....

marinatlas · Jun 19, 2009

Hi there, though not cheap I had ordered a set of rods/pistons from Jim Schmidt, will help to reduce the vibes in my Atlas with Commando engine, not yet received them but as soon as , will post some feedback, though it could take long , cause I need to have the crank rebalance (was std atlas at 84%), and will have it make by Pete Lovell, if he agrees (he did before!!)........

Connecting rods

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