big end located vs small end located rods

[vij]

Does some one have the measurement how wide the bigend located and the smallend located rods are in the bigend?

How much clearance should it be between the rods when they are installed on the crank shaft on a small end located engine?

Jocke..............

[brad black]

big end located rods are 22mm at both ends. small end located rods - 916/996sps, 996, 998, 749, st3, 748r, 748sps including all production ti rods - are 21mm at both ends. the wacky mid '90s corsa rods - the first small end located ones - are 21mm at the big end and 22 at the small end.

there is generally 2mm or so side clearance at the big end with small end located rods.

[vij]

Originally Posted by brad black

big end located rods are 22mm at both ends. small end located rods - 916/996sps, 996, 998, 749, st3, 748r, 748sps including all production ti rods - are 21mm at both ends. the wacky mid '90s corsa rods - the first small end located ones - are 21mm at the big end and 22 at the small end.

there is generally 2mm or so side clearance at the big end with small end located rods.

Thanks Brad.

Jocke...........

[vij]

Originally Posted by brad black

big end located rods are 22mm at both ends. small end located rods - 916/996sps, 996, 998, 749, st3, 748r, 748sps including all production ti rods - are 21mm at both ends. the wacky mid '90s corsa rods - the first small end located ones - are 21mm at the big end and 22 at the small end.

there is generally 2mm or so side clearance at the big end with small end located rods.

Hmmmm. This is not good. Mine are 22mm in both ends. The problem is that my nice 955 pistons are also 22mm.

I just start to realize that my rods will be both big end and small end located. Not good I guess. I have about 0,35mm axial movement between the rods on the bigend. It is how ever "centered". What I mean with this is that I can move them in both direction so in the crank so it is no side ways load on them. How much axial play do I need? Any one having experience of this?

Jocke.........

[brad black]

i've got a nice set of carrillos that'll fix your problem just fine.

my measurements were from memory, i'll try to dig out some rods and do it properly for you.

[vij]

Originally Posted by brad black

i've got a nice set of carrillos that'll fix your problem just fine.

my measurements were from memory, i'll try to dig out some rods and do it properly for you.

Thanks for the offer but I manged to sort it out. I got some figures from Schnyder Corse were I bought the rods.

I was thinking that it was not possible as the crank is in the engine but I actually managed to get the rods out, machine or should I say sandpaper them down.

Starting from about 21.85mm to 21,11mm using a very flat table and using 200, 240, 400, 600,800 and finally 1500 wet sandpaper lubricated with WD40 (about 20 hours job as I did it by hand).

It turned out perfectly flat and the rods last about 2,5 grams eash so I think the balancing is not totaly distroyed. Now the play is 1,95mm in the bigend.

I also managed to install the and TRQ them up. Not easy with the crank in the engine. Luckily it was carrillos so TRQ:ing is done be measuring the bolt stretch and that makes life so much easier.

Anyway thanks again for the advice and the offre.

Jocke.........

[acruhl]

I have a little bit more info here.

I had no idea that I had a problem similar to this when re-assembling my engine, and the end result is that for whatever reason, the rings won't seal and I'm blowing a lot of oil (it selaed fine before with the same pistons and rings, go figure). I was advised not to use new rings, BTW.

The story I have is that my pistons were cut to fit "Carillo rods". Apparently the small end on some Carillo rods is wider than Ducati rods, or maybe they all are 22mm? I don't know.

I also thought that there is a decimal in there, so not 21mm but 21.3mm or something? Not sure.

I don't have Carillo rods, but I do have SPS rods which are 21mm. My pistons are something like 23mm on spacing. They were cut to be wider, which you shouldn't need to do on a 996. I had no idea that this was a problem, being a total newbie. Also means that these pistons were never meant for this engine, one more way I got screwed by buying this bike. Live and learn.

New pistons will be on the way when I stop moping around, and I'm also going to put new bushings in the little ends. I have to take the crank out to do this, but I'm damn near an expert at that by now

[marvin]

just take a mill and widen the gap in the pistons, use the big end located rods.

[brad black]

carrillo make perfect copies of ducati rods, meaning they will make big end located, small end located or the mid '90s rods like i have. someone has just modified the pistons you have to suit big end located rods.

pull it all out and send the pistons and rods to bruce and he'll make spacers up to run what you have now.

pity you fixed yours vij, i would have been very intersted in a swap. i want some big end located ones for a 851.

[acruhl]

Actually, Bruce was the one who told me the Carillo story. Since these are 98mm pistons, they belong to a 996 motor, which always had little end located rods as far as I know. These pistons were cut for rods that they didn't belong with. So someone had some mish mash of parts at some point and put it together. Unfortunately, these pistons were used and installed into my engine (the wear marks on the pistons don't match up to the marks on the cylinders). One more problem I encountered too late.

These pistons are a little too worn, I was hoping to just put in a few races on them and then get new ones, but I'm getting new ones sooner rather than later.

Ran good until it started pumping oil though...

[brad black]

chris steedman has also had that - small end located rods, big end located pistons. he too said it ran fine, but had lots of blowby once they got it out on the track.

[acruhl]

Heh. Blowby is not the term I would use for what my bike was doing...

When I took the vertical head off, I was literally mucking black colored half burnt/half wet oil out of the exhaust port with my finger. It was pumping oil out of it.

Which is another reason for new pistons, rings, and I think I'm going to send them and the cylinders off to make sure everything is OK.

[chris steedman]

Originally Posted by brad black

chris steedman has also had that - small end located rods, big end located pistons. he too said it ran fine, but had lots of blowby once they got it out on the track.

the bike in question was a ti rodded 748sps wich someone did a diy 853 conversion on using incorrect pistons.

that engine lasted 600 miles !!!!!

when i got it apart i found somone had used small end located rods on big end located pistons . the massive side play caused the rods to eat themselves the pistons were also moving around too much causing blowby and they were also kissing the head by rocking sideways even though squish was over 1mm.

he had a big BILL for his stupidity.

dont risk it.

[acruhl]

Well, my rods pretty much ate themselves too. They contacted each other and the big ends were out of round. Fixed that. Now I need to change the bushings on the small ends. That along with pistons should probably do the trick. I hope.