shell sizes?

[Rarebear]

Hi there, work is proceeding slowly on my rebuilding efforts on the TRX850 motor for my XTZ s10, my biggest stumbling block is the people at my local Yamaha dealer!! the crank journals are chewed out and will need to be ground etc etc.... I'm trying to find out the dimensions of the the four different shell sizes yamaha offer, then the local crank specialist can acertain whether the crank is servicable or not.After several weeks trying to get the info out of the local spares "experts" i'm still in the dark. There is another specialist that does crank shaft 're-surfacing', but from the people i've spoken to seem to think that this is'nt a good long term solution. Please help!!!!
I have the motor stripped and am slowly collecting extra's so would like to get things moving. thanks for any help in advance.
rarebear

[pbear62]

Hi rarebear, We're not related are we? Not having any info at hand about the crank & brgs available for TRX's (hope I never need to either!) I wonder if Yamaha actually make undersize brgs available? A lot of Japanese cars & bikes have heat-treated cranks (niterided/tuftrided etc) which are not meant to be ground to an undersize (the heat-treatment is only a few thou thick & the shaft is "soft" under the heat treated outer layer) There are some companies who can re-heattreat shafts if necessary after grinding however a lot of the manufacturers don't consider this as a repair proposition & therefore don't make undersize brgs. Toyota for example, make brgs in sizes 1 thru 5 but these are all STD brgs with .0005" differences in thickness so exact clearances can be obtained during assembly. I've often seen engines fitted with different brgs in each conrod ie: One rod will have #1 brgs & another may have #4 for example - depends on the rod bigend sizing etc.
Like I said, I'm not sure what Yamaha did with the TRX - "normal" undersize crank brgs are available in .25mm, .50mm & .75mm sizes - better check what system they used before you go to the trouble of getting the crank ground!

[pbear62]

Oh yeah, another thing - re: crankshaft reclaiming/resurfacing. There are a few different ways of doing this too. (some better than others) I would probably steer away from getting the journals metal sprayed but there are people who do hard chroming of crankshafts. The engine reconditioner I used to work for, used to do this on a regular basis with no problems but then we purchased a GLEASON crankshaft welding machine from the US & this gave better results still. We used to reclaim cranks on everything from tiny Honda stationary motors, Kawasaki ZZR1100's, sprintcars etc right through to V12 CATs etc. This method leaves the crank journal with the original factory hardness & would be the best way to go if you can find someone over there who can do it. If not, I believe Southside Engine Reconditioners in Myaree (WA) now own the machine we had & I'm sure they would be able to help you. Let me know if you want me to chase this up for you if this is the way you want to go.

[Rarebear]

Gday Pbear, Thanks for the info, yes yamaha do exactly as you describe, they don't actually make undersize bearing shells just 4 different "coloured' shells for matching the tolerences perfectly. I was just hoping that the largest size shell would be appropriate for the crank after it has been ground. I will ring the people who do the crank re-claiming and talk to them about the processes that they use, now that you have given me the heads up. Thanks mate really appreciated, oh catchy name.....

[HansJ]

I tried to get infos on the sizes, but didn't succeed. Even the difference in colours was, IIRC, available for us humans... The workshop manual just says take this number from the crank, minus the nr from the crankhouse casing, the nr corresponds to the colour one should pick. I made several measurements with different shell colours, and to be honest, the difference between the colours were too small to be measureable, at least with Plastigage (which admittedly is a crude method...).

[pbear62]

If Yamaha only do std size brgs in different colours as you say, the difference between the thinnest & thickest shells will only be a couple of thou in total & only suitable if you're able to polish the shaft. If it has any sort of damage to the journals you're going to need to reclaim the damaged journal & then use the correct size/colour brgs - sometimes we used to find that the exact colour/number shell we needed weren't available in Australia so would then have to get the closest ones that were ex stock & polish the journal to get correct clearances. May be best to find what colours are in stock, buy them & fit to your rods & then get the journal reclaimed to suit. Are your rods still OK? - if it's pounded the brgs the rod big ends maybe u/s as well - best to get these checked too.

[Rarebear]

Well i'm starting to get somewhere now, thanks for the help fella's. New crank [aus] $1700.00. New crank from the usa am finding out about now. Build up the journals and re hard chrome around $200-$400 per journal, or re-metalize, he's getting back to me about. The bloke tells me that they have no problems with this treatment on motors that run much higher pressure than the TRX. Theres different treatments, powder spray and forgotten the other one, applied with a pray at around 8000psi.
As far as the con-rods go, just had a look at them and where there is a silver type coating on the inside of the rod ends that has worn off and exposed a black type colouring, there is no gouging though, is this still okay?
What is everyone else doing with there blown up TRX's!!?? For a bike that seems to be very prone to this problem i would have thought this forum would be over run with this topic?

[pbear62]

Hi rarebear, Not having seen one of these motors in bits myself, I'm not sure about the colour you mention on the rods. The only way to be sure of the condition would be to get someone to measure the ID of the rod tunnel & check for "out of roundness" - sometimes the rods can look perfectly OK but they only need to be a couple of thou out of round & it will fail again in no time.

[Quan-Time]

OK... TRX (and for that fact most yamaha bikes) go in COLOURS.. not actual sizes. From memory BLACK is the thinnest, and GREEN is the thickest.. Theres 5 colours in total. Id have to double check the chart to see which one is which. But the actual thickness difference is bugger all.. They mainly work for rebuilding. Whatever your stock colour is (what you pulled out) thats what you re-order.. you dont order "0.05mm oversize" bearings...

Your best bet is to take a sample bearing to an engine builder (car engine) and say "my crank has been re-ground this much.. can you help source some bearings to suit ?".. You would be surprised.. You can get custom bearings made fairly easy nower days. Im 100% positive COME racing in victoria can hook you up.. http://www.comeracing.com/ But you obviously wanna find someone local... Shoot em an email and at least find out your options.

Hope this helps