PE 400 vs RM 400 bottom ends?

[Bruno1969]

Here's the reason for this question!

At our last VMX race I lent a mate my 78 RM 400 as I was still injured after the last round when my ambitions exceeded my talent.

This is what happened;

First race of the day ; my mate got a good start, halfway down the straight as he hooked third...a huge bang that I could hear from the side lines and the bike stopped dead going from pretty quick to no where instantly.
 
I was wondering why my mate appeared to be crying or praying next to the bike while on his knees....Turns out he smashed his nuts on the tank with the dead stop and was waiting for the waves of nausea and pain to go away.
 
Stripped the motor and the (original Suzuki) rod snapped just below the small end.

Can't figure out why the rod let go like that - was a brand new rebore, piston, rings, small end bearing and gudgeon pin. Can only be some wear in the small end bush ( but didn't feel like it when I assembled the motor) or just metal fatigue on the original rod ? What say you fellows?

Next question - what differances are there, if any between the 78 RM 400 bottom end and the PE 400 of the same years, say up to 81? As far as I know, the PE barrel is pOrted a little less agrressively and the gear ratios are a bit wider but thats really it?

[TM BILL]

Unfortunatley they are completley different , the closest bottom end to yours is RM 370 .
But rods are a bastard to find  There is a bloke over here who has remanufactuerd rods for RM 400s N and T models .
If he gets enough orders he may do a run of 370 / 400C rods .

[suzuki27]

What about the US mob ,Anchak and sons or something like that. Didn't he do a run of rods etc for these?
Does the crank still turn? Any other signs of a big seize in the cylinder? Sounds like an odd break for sure.

[TM BILL]

No just pistons etc

http://www.anchakandsons.com/rmparts.html

[oldfart]

post the dimensions     A   B  C  D  E  F  H  I 
A = small end bore 
B = big end bore
C = centre to centre
D = small end width
E = big end width
F = over all length
H = B/E pin dia
I =  B/E pin length
As I'm currently doing a search for a  rod  ( different application )   and have a shit load of imfo I need to wade thru over the next fe days  and may come across one

[oldfart]

The Pe 400 is sourced from a Sea-Doo 650  1997   ( hot rod part # 8117 )   
A = 125
B = 25
C = 31
D = 17
E = 17
Big end bearing 24x 31x 17

[Bruno1969]

Thanks for the quick replies fellows!

Sods luck it seems in not being able to source a rod and just my luck that PE stuff isnt even close! Next question ...would a PE bottom end work with a RM 400 barrel or even a whoel engine slot into a RM 400 frame?

The piston is completely free in the barrel..everything had a nice oily sheen to it so it wanst any kind of seize thats for sure!

Old fart - i need to split the cases the flywheels before i can get you that information.

Oh the joys of VMX....

Regards

 

[Marc.com]

Thanks for the quick replies fellows!

Sods luck it seems in not being able to source a rod and just my luck that PE stuff isnt even close! Next question ...would a PE bottom end work with a RM 400 barrel or even a whoel engine slot into a RM 400 frame?

RM bottom end as Bill said is completely different to PE gearbox and casings, why not just use the whole PE motor, it gave virtually the same hp as the RM400 and you gain primary kick starting and later design. Swapping motors should not be a drama.

[TM BILL]

Maybe talk to TT5 Matt as he mentions in this thread he has RM 400C bottom end 

http://ozvmx.com/community/index.php?topic=24553.0
Re: klx250 82

« Reply #3 on: July 10, 2012, 11:13:09 AM »

Quote


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yes dono ive got them aswell, 2x rm125s 1 a low hr bike with orginal tyres/chain and is still on std piston rings,a rm125m,ts125 and a ts100A and maybe my fav with bent back forks which by the way helps the little forker corner a ts185A.then theres a rm250b and rm400c bottom ends so yeah ive got some suzukis too

[Lozza]

 
Stripped the motor and the (original Suzuki) rod snapped just below the small end.

Can't figure out why the rod let go like that - was a brand new rebore, piston, rings, small end bearing and gudgeon pin. Can only be some wear in the small end bush ( but didn't feel like it when I assembled the motor) or just metal fatigue on the original rod ? What say you fellows?

Bore/stroke are different from the PE to RM not much interchangable. Rod would have snapped from over reving, the PE has the short stroke big bore.

[Bruno1969]

Thanks for all the help lads.

I think the short term answer, because it is sheeeet loads easier to find one, is to get a PE 400 motor and slot it into the frame while i take my time and get the RM motor sorted.

[TM BILL]

I dont think a PE motor bolts straight into a 400C frame without changing front and rear mounts. PE motor will bolt into 400 N/T frame if you change front mount .

[Bruno1969]

Thanks TM Bill.

Either way I look at this, its not going to be an easy, cheap or quick fix.... :'(

[TM BILL]

Thanks TM Bill.

Either way I look at this, its not going to be an easy, cheap or quick fix.... :'(
[/quote

I wish i could offer somthing positive  will keep an eye out for a rod or bottom end for you 

[bigk]

Can't remember the exact details but we fitted a YZ465/490 rod to an RM400C a while back. Wasn't a difficult conversion.
K