New con rods from MAP or keep the stock ones?

tompkins · Apr 17, 2026

R&R rods are lighter than stock @ 400 grams and are bushless like a norton rod, so less small end weight? - stock ones averaged out to 420 grams when I weighed em. Map are heaver @430 grams, Hepolite marginally heavier yet @ 432 grams. LF harris say they're OEM, but nobody lists a weight, and I can't find 'em stateside. I'm thinking whichever way I go it's like 10 grams difference totally, probably less than that on the little end... so no big deal? total over both rods would be 20 grams more if I went with the steel MAP rods. the difference would be 40 grams less with the R&R. If I guy was to roll the dice and just run em no rebalance, would you go less or more weight and why? Balance factor goes down when the rod weight goes up and vice versa... assuming the crank was actually factory balanced to 85% heaver rods would move it closer to 80, lighter rods closer to 90... any thoughts? Also, im more inclined to not care so much since the rods that were in it were 6 grams apart to begin with...

Onder · Sunday at 8:31 AM

Hello? Was there any answer to your questions? I am in the same place right now so I would like to know.

Fast Eddie · Sunday at 9:05 AM

Onder said:
Hello? Was there any answer to your questions? I am in the same place right now so I would like to know.

What are you wanting ‘em for Onder ?

concours · Sunday at 9:10 AM

" I guess that the modern detergent oil went to work breaking down the sludge in the probably jam packed trap and pumping it through the motor."

Very real and oft repeated "self inflicted wound"

Onder · Sunday at 10:03 AM

concours said:
" I guess that the modern detergent oil went to work breaking down the sludge in the probably jam packed trap and pumping it through the motor."

Very real and oft repeated "self inflicted wound"

I mount the pulpit : Never start the bike up and see how it goes. Instead strip it and see how it is. So much cheaper and
easier in the long and even not so long run.

Onder · Sunday at 10:12 AM

Fast Eddie said:
What are you wanting ‘em for Onder ?

I want rods for a T150. Stock rods I have are 8 grams apart. They are not from the engine abuilding rather just bits collected over too many years. Hepolite steel rods appear to be the cheapest set on offer. They claim to be with in one gram of each other but they do not specify the total weight of each rod. And they claim to me be in the UK.
Trying to keep this within sensible financial bounds but you know how that goes...

Fast Eddie · Sunday at 10:59 AM

Onder said:
I want rods for a T150. Stock rods I have are 8 grams apart. They are not from the engine abuilding rather just bits collected over too many years. Hepolite steel rods appear to be the cheapest set on offer. They claim to be with in one gram of each other but they do not specify the total weight of each rod. And they claim to me be in the UK.
Trying to keep this within sensible financial bounds but you know how that goes...

Thunder Engineering alloy rods…

Onder · Sunday at 11:23 AM

Fast Eddie said:
Thunder Engineering alloy rods…

They are in my current T150v. No issues. But price come into it....

Onder · Sunday at 1:16 PM

You must have wondered at some time why the modern bikes usually use steel rods. Because you don't have to worry so
much about scratching the rod during install?

tompkins · Sunday at 7:21 PM

Onder said:
You must have wondered at some time why the modern bikes usually use steel rods. Because you don't have to worry so
much about scratching the rod during install?

Aluminum has so many stress cycles before it gets fatigued and liable to punch out the cases. I went with the MAP steelies, haven’t noticed too much difference in vibes but I’ve only took er down the freeway once. Very docile around town and on the back roads. Idk with a 3 pot bike though- the imbalance would be multiplied by 3. Although my t150 was quite smooth, so you may never notice like you would with a twin

tompkins · Sunday at 7:24 PM

Also, you’re a braver man than I going to the crank on a 3 banger- I got rid of mine before it came to that

Onder · 2026-08-27T08:07:33-0600

Received the Hepolite steel rods. I did not unwrap them from their plastic blanket and little pack of silica gel.
Weighed them in : 426.0 426.2 426.3 . We will give the scale a 1/10th gram variation although I weighed each
one three times. Weight of the stock rods: 397.8 399.6 406.0 393.9 . No, I do not have a secret Quadrant,
just the rods I had to hand. Weight of the Harris big ends shells 34.5g.
I must say I immediately noticed the weight difference upon picking the new rods up. Did not weigh out the
small ends though I really should suspect that the steel rods are not that from from the stock ones.
As Im not really up to send out the crank for rebalancing , leaning toward a return on the steel rods and replace
with the R&R ally ones. Previous poster says 400g a lot closer to stock.
Am I over thinking this? Opinions welcome...
Edit: And wot about balance in terms of over and under, where does that move the sweet spot to?

Fast Eddie · 2026-08-27T09:00:22-0600

Onder said:
Received the Hepolite steel rods. I did not unwrap them from their plastic blanket and little pack of silica gel.
Weighed them in : 426.0 426.2 426.3 . We will give the scale a 1/10th gram variation although I weighed each
one three times. Weight of the stock rods: 397.8 399.6 406.0 393.9 . No, I do not have a secret Quadrant,
just the rods I had to hand. Weight of the Harris big ends shells 34.5g.
I must say I immediately noticed the weight difference upon picking the new rods up. Did not weigh out the
small ends though I really should suspect that the steel rods are not that from from the stock ones.
As Im not really up to send out the crank for rebalancing , leaning toward a return on the steel rods and replace
with the R&R ally ones. Previous poster says 400g a lot closer to stock.
Am I over thinking this? Opinions welcome...
Edit: And wot about balance in terms of over and under, where does that move the sweet spot to?

If it were me, I’d go for the lighter option.

If I were building something hot enough to benefit from steel rods, I’d go Carrillo.

But assuming you’re not building a 100bhp hot rod, the lighter alloys will be more than man enough IMHO.

Steel rods will outlast alloys in terms of fatigue… but you ain’t gonna live long enough to worry about that !

IMHO triples do benefit from dynamic balancing.

Onder · 2026-08-27T09:11:06-0600

It is 165 quid more for the alloy rods. That is a fair amount but if I keep the steel rods I would have to rebalance the crank and
that would eat up the difference Im sure.
Will be running 850 pistons so more weigh piled on. Will wait and see what the Commentariat advise but looks like they will
be returned.
Poor planning on my part. ...AGAIN!

Fast Eddie · 2026-08-27T09:50:44-0600

You plan ?!?

Onder · 2026-08-27T11:19:41-0600

No plan survives contact with the enemy.......er, that would be ourselves!!

Schwany · 2026-08-27T14:07:49-0600

I have a two car garage full of stuff I didn't plan for.

ESO-terix · 2026-08-27T17:17:02-0600

tompkins said:
Aluminum has so many stress cycles before it gets fatigued and liable to punch out the cases. I went with the MAP steelies, haven’t noticed too much difference in vibes but I’ve only took er down the freeway once. Very docile around town and on the back roads. Idk with a 3 pot bike though- the imbalance would be multiplied by 3. Although my t150 was quite smooth, so you may never notice like you would with a twin

New con rods from MAP or keep the stock ones?

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