Help FZR250 Rebuild but cant source conrod bolts?

i know some of this some of the time. Not infallible.
But what is consistent with Honda is that all 6mm big end bolts will have the same shank OD.
Same with 8mm. I found a long enough bolt - CB1100R - to fit the RC30 and sure enough the shank OD was the same.
It's called sensible design practise. All rods using that size bolt are finish reamed to the same ID - probably on the same machine. The designer can go to his table of rod bolt lengths , pick a length that suits - and the drawing probably dimensions itself from a table of standard practise dimensions.
Other companies don't seem to have this consistency.

 

Not TTY bolt. TTY tightening sequence typically requires tightening to 50-60% of yield, then relaxing to 20-25%, then tightening back up to spec.

Those are only needed for interfaces with wide-range of stresses such as alloy head on iron block. The huge expansion range of head (+/- 0.25mm in some cases), causes large cycling loads on head bolts that causes fatigue failure. Using TTY puts them into more stable plastic region just below yield limit.

On these rod-bolts, there's no need for TTY as interface is stable once bolted together. Torque sequence is simple and linear.

 

Another potential candidate - the local Honda dealer has not bothered to respond

https://www.kawasakionlineparts.com.au/partFinder/fiche/kawasaki/1999/zr250-balius/crankshaft#next

https://www.kawasakionlineparts.com.au/part/kawasaki/921501249#content

One thing to note - the crank pin diameter on the ZXR250 is 25mm, whereas the FZR250 is 27mm - this may affect the conrod bolt length and make them too short

Online stock checker isn't working...

 

It's been gnawing at me also - last piece of a very complicated puzzle for me

The Kawasaki ZR250 [ZXR250 also] conrod bolt is actually listed as 6mm, however as mentioned they use a 25mm conrod crank pin, which may mean that they are shorter, but I am hoping that they're long enough - all other elements being equal

Checking the blurry picture from this auction - I get the length to be ~35mm -36mm

https://www.ebay.com.au/itm/202722668542

 

I wouldn't buy a full set of 8 on spec without knowing the length either - those Kawasaki nuts should work -
https://www.kawasakionlineparts.com.au/part/kawasaki/920151769#content

I've just measure two FZR250 conrod bolts which I have here - they are definitively 5.98mm on the locating section [shank].

I'm going to enquire with ARP re: custom bolts - it would be good if we could get the measurements from a CBR250rr and a ZXR250 to see if those bolts are the same in the critical [shank] dimension of 5.98mm

 

So I've just put eight of the MC22 bolts an nuts into the shopping cart with cmsnl - comes to 72 Euros for the parts and 36 euros for shipping - YEAH RIGHT! - that's $171AUD

https://www.cmsnl.com/products/bolt-connecting_13213kaz003/
https://www.cmsnl.com/products/nut-connecting-ro_13215kaz000/

Now we know they're coming up and NLA anyway, so I won't bother...

How much would a set of custom ARP bolts and nuts come in at?

I haven't found and email contact or form for custom orders with them yet - only a phone number to call.

One thing which occurred to me is the new Kawasaki ZX25R - it's been released in several markets now, but there is next to no information on actual parts via google, it's all BLING - it's jewellery for bikes

Motorcyclists - well not tarring everyone here with the same brush, but DAMN they do love BLING!

 

DANG I was about to order 1 bolt and nut for measurement
This reminds me of when my mate and i tuned his Celica - plugs, points, and adjusted the ignition timing, then when he was tightening the distributor adjustment locking bolt he used too much elbow

DANG car useless for want of 1 bolt - we got a replacement easily though

Similar here - rebuild stops because of 1 bolt - NLA - Yamaha the buggers!

 

I have box of MC19 leftovers. Let me see if there's con-rod bolt...

 

Would love for you to make a measurement - shank diameter most essential - under head length should be suitable and from pictures that I have seen the heads look to have a little more meat to them which is good

FWIW - of all the manufacturers and various models that I have checked [LOTS!] - only Kawasaki seem to be available, Honda NLA, Yamaha NLA and Suzuki on one model the bolt is part of the rod assembly NLA, on later models based on the 4 Cyl 250, the bolt screws into the underneath of the rod directly and on some sites even those bolts are NLA

 

MC 19 bolts are superseced by MC22 bolts - I expect 1mm length difference - I'm trying to gauge whether or not there would be sufficient interest across the different makes/model to justify a custom order for a manufacturer ARP or another - if the bolts are interchangeable between the ones that we have surveyed that's a win - there may be other users on other forums that will consider a set given they are NLA and the price per set will come down accordingly

 

Sorry, no con-rod bolts in my tub of nuts & bolts.

 

On the one FZR250 conrod that I have in front of me, there is slight movement on one side with the conrod, so the hole is over the 5.98mm of the machined part of the shaft - the other side has a small amount of something in the rod upper and is tight in that side

I reckon these will fit/push/press straight in without the need to ream the rods and will actually fit better than the FZR250 conrod bolts

Most importantly the under head length on the FZR250 bolts is 35.5mm, the ZXR250 bolts under head length is 37mm - winner - they are long enough

 

There is space for movement with the standard fzr250 conrod bolts - the heads have clearance to turn a little - I don't think there will be an issue with the Kawasaki bolts - at most if the bolt head doesn't go down to the machines recess on the rods it would take removing a tiny amount from the outer edge of the recess where it angles down

Have a look at one of your rods to see what I mean