Anybody here press new rods into cranks?

Brandon Weiss (Detective brandon to you) /

I'm trying to weigh my options here...

Not a moped, but it's close enough i think.

I have a Cimatti 86 with a 4 speed minarelli p6 that needs either a new crank, or a new rod. While there is no in and out play of the rod (at least what i can detect) it moves side to side more than i am comfortable with, and with the new cylinder kit it will be getting i'd like to do something about it. The cranks are difficult to find for the 4 speed variant of P6, and the ones that are out there ring up to almost $200 with shipping from Europe.

I can get a rod for about $100, but i'm unsure what it would cost to have it pressed in.

The big question is, can i get away with just replacing the bottom end bearing of the crank, keeping the rod? The bearings are cheap, and it would save me a whole lot of money. I'm just unsure of what typically wears, the rod or the bearing, or both....

This will not be a race bike or a daily rider, rather a fun toy to take on rides occasionally.

Any ideas?

Here are the specs of the rod, in case you may know of a compatible one from another bike that would be cheaper:

85mm center to center, small end is 14mm wide, takes a 12x15x15 needle bearing.

Big end takes a 16mm ID needle bearing and pin, same width as the top i think.

Re: Anybody here press new rods into cranks?

Jimmy Cincinnati /

I would only rebuild with a complete conrod kit, replacing just the bearing would be a bad idea. There are some shops on ebay that ive used that are cheap and decent.

https://www.ebay.com/itm/Motorcycle-ATV-Crankshaft-Crank-Rebuild-Service-CRF-YZF-KXF-RMZ-CR-YZ-KX/152999244410?epid=914943547&hash=item239f77327a:g:iCEAAOxydUJTNe92:rk:2:pf:0

Re: Anybody here press new rods into cranks?

Brandon Weiss (Detective brandon to you) /

Here are 2 close candidates i found on treats.. a vespa rod, length is only 1mm longer, but its pretty thin on the ends at about 10mm....

And a puch rito rod.....closer in the thickness department, but it's 5mm longer at 90mm. I suppose i could make a base spacer for the cylinder?

Re: Anybody here press new rods into cranks?

Brandon Weiss (Detective brandon to you) /

Re: Anybody here press new rods into cranks?

Dirty30 Dillon /

If there's no in and out play, than I wouldn't risk trying to have someone else rebuild it, especially not with a non-specific built rod.

The big end bearings will have 1-2mm of lateral movement at the small end, and that's fine.

I would run it as is, no questions asked.

Re: Anybody here press new rods into cranks?

What's up

20190130_142159.jpg

Re: Anybody here press new rods into cranks?

What makes you think you'll be any farther ahead with a different rod ?

The rod needs side play to insure proper alignment with the piston .

The only thing that would be of concern is if the rod rocked side to side , as opposed to straight sliding or slipping .

But , it's your money and time .

Re: Anybody here press new rods into cranks?

And if you spent a hundred in parts and then had to pay someone to press it in, what are you saving? Run as is

Re: Anybody here press new rods into cranks?

Dirty30 Dillon /

> Tri-ped Dave Wrote:

> -------------------------------------------------------

> And if you spent a hundred in parts and then had to pay someone to

> press it in, what are you saving? Run as is

Dave has personally owned P4/P6 motors and worked on them heavily, I would defer to his knowledge any day.

Re: Anybody here press new rods into cranks?

Brandon Weiss (Detective brandon to you) /

> Tri-ped Dave Wrote:

> -------------------------------------------------------

> And if you spent a hundred in parts and then had to pay someone to

> press it in, what are you saving? Run as is

My rationale was ensuring the safety of the very expensive cylinder and head i will be putting on it in the future. The Crankshaft bearings (the ones supporting the crank) are on their way out, and i will be rebuilding the engine before i run the kit anyway, so i figured i would try and get a new rod or crank. But i guess i'll just run with what i've got.

Re: Anybody here press new rods into cranks?

♣Slew Foot♣ /

Out of five one didn't fry...

Tiny amount of axial play and copper washers and hi temp non seize lube.

Re: Anybody here press new rods into cranks?

Mrcrankshaft.com

Re: Anybody here press new rods into cranks?

how much axial play are we talking?

and what is the spec?

with no radial play and no rocking you are in the ball park, i agree with everyone who says run it, but curious what the numbers are. especially on a roller bearing with bushings, can't imagine this will be high on the list of things that detonate.

Re: Anybody here press new rods into cranks?

♣Slew Foot♣ /

Not detonate but hard seize due to frictional heat and not enough room to let fuel lube it.

Re: Anybody here press new rods into cranks?

Brandon Weiss (Detective brandon to you) /

fyi, this has a needle bearing big end rod....not bushing. I'll document the rebuild and make a thread when i get around to it.

Re: Anybody here press new rods into cranks?

♣Slew Foot♣ /

I can show you even with a needle bearing. It needs lube at that lower more than the upper. It basically rocks back and fro creating oval needles w/o the lube and teensy bit of axial play on the con rod it can also buck out a circlip by constant repetitive stress

Re: Anybody here press new rods into cranks?

Darrell Chapman /

Hi guys a newbie here in Reno. I work at a large Powerhouse Honda dealer and I rebuild crankshafts. Typically side clearance on rod big end is .010"-.030" for two strokes. We charge an hour at the shop normally which is $85. If you want it done message me and we can talk about it. I've worked there for 14yrs and have a Red Level Honda certification if that helps?

Re: Anybody here press new rods into cranks?

🇮🇹💦 Of the Loin /

minarelli v1 shares a con rod with either the P4 or the P6, I forget

but I guess that doesn't help because I usually bought the P4/P6 conrods to rebuild v1s with...

Re: Anybody here press new rods into cranks?

Brandon Weiss (Detective brandon to you) /

> Maitland Of the Loin Wrote:

> -------------------------------------------------------

> minarelli v1 shares a con rod with either the P4 or the P6, I forget

>

> but I guess that doesn't help because I usually bought the P4/P6 conrods

> to rebuild v1s with...

That's one thing i was curious of, thanks for that good bit of info. DOS hooked me up with the above pictured rod^^^^^

Re: Anybody here press new rods into cranks?

Jimmy Cincinnati /

If you run it as is, cool. Hope it works out.

But if your going to replace the rod & lower bearing than i would also replace the pin. The pin could be grooved / damaged just like the bearing & rod.

Re: Anybody here press new rods into cranks?

does mopedcrankworks still exist? I had them do a few cranks, oddballs that were hard to replace and also for converting ZA to rollerbearing. Great work and cheaper than a whole new crank.

Re: Anybody here press new rods into cranks?

Brandon Weiss (Detective brandon to you) /

> Jimmy Cincinnati Wrote:

> -------------------------------------------------------

> If you run it as is, cool. Hope it works out.

>

> But if your going to replace the rod & lower bearing than i would also

> replace the pin. The pin could be grooved / damaged just like the

> bearing & rod.

Of course! This rod didnt come with a pin, but in the event i need to use the new rod and send it out, i'm sure whoever i send it to will have plenty of 16mm pin stock. Or, i can just measure the existing pin and buy a replacement to send with it.

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