Another crank gone!!

[misterdimwiddy]

A quick report on my day of high and lows at Brands this Thursday.

After extensive winter mods including;

YZF rear + 5.5" wheel
FCR41's (dyno'd a week ago at 88rwhp; 60Nm)
Replacement clocks, fairing etc

My track only TRX was just about complete apart from some head work and perhaps cams this winter coming.

Wet start at Brands and slithered round like an old woman on brand new Pirellis. Then popped the wets I've never used on (Bridgestone Battlax Racing) and the fun started. Anyone that has never ridden on wets, I cannnot recommend them more highly.

Phenomenal grip and a feeling of such confidence that within 3 laps I was riding round the outside of everyone in the inters group, only being passed by one fast bloke on an R6 also on wets and I was not far off his pace. I have never enjoyed wet weather riding but it is almost more fun than riding in the dry, picking people off and wondering where the limit of grip really is. Amazing and a good way to save the day when your long awaited track day turns out to be wet.

The FCR's were the next revelation. Tremendous power, excellent feel and a wonderful sound. It is like a completely different bike and is sooooo fast. Perfect power delivery in the wet as well and so easy to wind it on out of the turns while the strokers and litre boys are fearful of highsiding.

Track dried up during the afternoon and back out on Pirellis until the final session..................when it all went bad. Felt vibes through the pegs coming out of Druids and thought "doesnt usually feel like that". By Bottom bend it felt like it was going to conk out so limped back to the paddock.

Ear plugs out and quickly turn it off due to unmistakeable rumble from bottom end. Crap.

Head and barrels off this evening show no damage to the cams or 878 kit. Phew.

Left hand rod however moves up and down noticeably and once the generator cover came off it became clear that the main bearing that side is also shot to shit. Wear apparent on small ends/gudgeon pins as well which has to suggest lubrication issues.

I drained 4 lires of fresh new Castrol out so no oil level issues. Perhaps the pump has died or alternatively, what is a high mileage bottom end has finally had enough now I'm close top 90hp and spending most of the time near the red line.

The oil light has been showing at low revs when really hot. Maybe this is a tell tale sign that the crank clearances are getting baggy?

Feel a bit despondent as it was such a fantastic track bike in its final form.

Will split the cases and see whether I can get away with new shells but I fear the crank has had it.

So, what to do? Junk the motor, sell all of my goodies to you lot and buy a 675 Triumph or wait for another motor to come up and get back out there?

If anyone has a short motor or a decent crank + rods then I would be keen to hang onto it really. There's a TDM900 motor on ebay but not sure whether this would go straight in with my head and FCR's? Wiseco do a kit for these I recall.

I'm off to bed; can't face removing the motor this evening.

[sanddune51]

Phil, I'm really sorry to hear this. Please don't resort to breaking another Trx for spares. Chris Applebee in East Anglia can regrind cranks and supply bearings to suit. I think that would be my preferred option,depending of course what you find when you pull the crank out.
Hoping you're able to sort it.

Mark.

[Yoozy]

Sounds like you were having a giggle on the Rex before it puked, I loved my rip round Oulton on mine. It'll be better today mate and I think you should sort it and get it back up and running.

Dibs the fcr's if you don't though

[alextrx850]

Phil,..Whip the side oil pump cover off and see if the nylon gears that turn the two oil pumps have still purchase to their shafts...I might guess that a gear has sheared it's drive slot and stopped the pump pumping....noticed a slight sloppiness to the two drive gears recently when I was changing my cam chain ...they only have a circlip to keep them in place and a flat slot to give the drive...a weak point in my thoughts.

878 kit and cams pls

[misterdimwiddy]

Thanks for your comments and words of encouragement lads.

I am not in a great hurry to sell everything and will do my utmost to rebuild the motor so don't get too excited yet!!

The bike was quite a brute with the combined mods that I now have and embarrassed a lot of modern trick machinery.

I have got the rods off and the left hand side has spun its shells leaving very light damage to that journal. Looks repairable though.

I can't split the cases yet until I have got the clutch and rotor off. Plenty of slop in the main bearings may be a bad sign; lots of shell material in the sump.

It didn't run for long while knocking so fingers crossed.

Alex - I did have the pump sprockets off and they looked ok. It would be reassuring to know what caused the failure before it goes back together just in case it does it again! Still seems strange that both gudgeon pins are ridged; don't recall JE pins being stepped when I got them. Any useful info or experience anyone please? The small end of the rod measures up at 20mm and seem round and not obviously worn. Neither rod shows blueing from heat build up due to friction.

Mark - thanks for the regrind refereral; I will head that way if it does ultimately look repairable.

Will update on main bearing condition next week.

Sell it and buy a 675?? What was I saying..............

Phil

[misterdimwiddy]

Sorry to drone about my blown motor.

Just sat here with a brew staring into my open crank cases wondering what prompted the big end failure.

Would welcome any comment on the following line of thought.

No damage to bores or cam bearings suggests that oil was circulating where it should be + 4 litres of the stuff came out when I drained it.

Big end bearings spinning (in left hand rod only) suggests something caused this bearing to pick up but not the rh one. Not sure what yet.

I am now thinking that though there is considerable play in all of the main bearings (have yet to see the bearing surfaces or shell condition), perhaps this play has not been caused last week at Brands? More that it reflects the very worn condition of my bottom end (actual mileage unknown but probably 40-50k) and that it has run like this for some time. The crank at either cam chain or generator end can be moved vertically by about the same amount (difficult to quantify). When rotated there is no roughness at all in the mains. Bearing clearance is specified as 0.02 to 0.038mm with a service limit of 0.1mm.

Do worn mains sound like worn big ends (obvious deep rumble) and would it be possible to run like this without sounding chronically unwell? I've got a pretty good ear for unhealthy mechanical things and my Rex never sounded rough.

Wear to the mains would drop the oil pressure (as I understand it) and I have always had the (recently fitted) oil lamp showing at <2krpm when the motors hot. I always thought this was because the switched range of the VW unit is not correct for the TRX. Maybe it tells me that pressure actually was low (due to crank shell wear?).

Both balance shafts have similar amounts of radial movement at the bearing ends. Again makes me think it is just a well worn motor. These have needle roller bearings not shells and could be replaced.

Final piece of the puzzle may be that low oil pressure at the crank may have led to small end lubrication not being effective. These I believe are splash fed only from jets in the upper side of the rods. If my pressure was low than the gudgeon pin wear that I have could have resulted from this.

I may be clutching at straws but would be pleased if the main bearing journals are OK when the cases are split (this week) and that a set of main shells + big end regrind with oversize shells (£165) may do the trick and I'll be back out in no time.

Any experience you can provide of failed main bearing symptoms might convince me that my hypothesis is at all likely to be correct.

Thanks

Philby

[zednine]

Hi Philby

I have had 2 of these here for engine work and in both cases it was the left hand big end ( plus my own bike which was a snapped crank as a result of a crank repair needed when the left hand big end went )

In all 3 the mains were fine so Im pretty sure you will be ok

Why always the left though ? ....... is it just concidence ?

Chris

[rogerc41]

Oh mate gutted that you put so much effort in to only have that happen. I'm puuting a fair bit of cash and a whole lot of time into my restoration project at present and will be constantly on edge when its back on the road with all the bottom end knightmares i keep hearing about

If the left hand big end is gone, i'm pretty sure that the oil flows from right to left accross the crank (correct me if i'm wrong), so it being the second of the two to be lubed could point the finger, but then if that was the case it is weird that the cams are all good, as the feed then goes from the left side crank into the right side of the cams to supply them. And with the cams fitting directly into the journals in the head i dont think it would take much for those to pick up either!!

Are you able to check the oil galleries in the crank at all, like blowing them through with some compressed air to make sure there clear?? Or to see what comes out?? I see that you have an oil pressure switch fitted but have you ever checked the flow at the end of the cams by removing the blanking bolt?? I see a post the other day on here where someone was saying that they remove that bolt before every start, then crank the engine without the HT leads on to check the flow before starting.

Keep us posted on how things go, i really hope that it's all repairable.

[misterdimwiddy]

Hi Philby

I have had 2 of these here for engine work and in both cases it was the left hand big end ( plus my own bike which was a snapped crank as a result of a crank repair needed when the left hand big end went )

In all 3 the mains were fine so Im pretty sure you will be ok

Why always the left though ? ....... is it just concidence ?

Chris

Thanks Chris

This is positive news and suggests that I may be lucky yet.

Rogerc41 - I agree that if the LH rod is second in line for oil, this could perhaps see even lower pressure than the RHS leading to frequent failure. I also feel that the loading on the mains is less severe than the big ends and hence they tend to survive.

Oil flow from my gallery bolt was good shortly before the damage occurred.

I am filled with optimism and will now order a clutch holding tool to get the cases apart on Wed.

Quick observation for those considering engine work; you can get the rods out without splitting the cases.

Has anyone split their cases while leaving the balance shafts in and the rotor on the crank? Should have undone the bolt when the motor was in one piece!!

Will update you in a few days

Phil

[Tarwetijger]

I believe the rotor could stay on the crank, yes.
Not sure about the balance shafts. I suppose they drop out eventually anyway.

[misterdimwiddy]

You need to remove the rotor and starter clutch to get to the plates that retain the balance shafts.

Looks to me as though the cases would split and then I can hold the crank in a vice and remove the rotor bolt. Balance shafts would then be easily removed to assist correct alignment when reassembling.

I'll let you know if this is the case!

[zednine]

The rotor can stay on the crank but getting the bolt out is the easy bit ....... getting the rotor of the shaft is tough ,,,,,,,,, they are on very tight

You can make a removal tool easily enough using a piece of 6mm plate and and a pillar drill. The balance shafts can stay in the cases as can gearbox etc

[misterdimwiddy]

Hi Philby

I have had 2 of these here for engine work and in both cases it was the left hand big end ( plus my own bike which was a snapped crank as a result of a crank repair needed when the left hand big end went )

In all 3 the mains were fine so Im pretty sure you will be ok

Why always the left though ? ....... is it just concidence ?

Chris

Chris

Looking at the online manual, the LH big end is the last one in line for oil supply from the pump, it being fed through the third main bearing which makes you think that it would indeed have the worst conditions in a poor lubrication/low pressure scenario.

I will measure the main and RH big end bearing clearances as is with old shells to see whether I was outside the 0.1mm upper tolerance when it went bang.

[dixonj]

Hi Philby

I have had 2 of these here for engine work and in both cases it was the left hand big end ( plus my own bike which was a snapped crank as a result of a crank repair needed when the left hand big end went )

In all 3 the mains were fine so Im pretty sure you will be ok

Why always the left though ? ....... is it just concidence ?

Chris

Chris

Looking at the online manual, the LH big end is the last one in line for oil supply from the pump, it being fed through the third main bearing which makes you think that it would indeed have the worst conditions in a poor lubrication/low pressure scenario.

I will measure the main and RH big end bearing clearances as is with old shells to see whether I was outside the 0.1mm upper tolerance when it went bang.

You have pm

[misterdimwiddy]

The rotor can stay on the crank but getting the bolt out is the easy bit ....... getting the rotor of the shaft is tough ,,,,,,,,, they are on very tight

You can make a removal tool easily enough using a piece of 6mm plate and and a pillar drill. The balance shafts can stay in the cases as can gearbox etc

You are not kidding!!

Made a puller with an M16 socket cap bolt through the middle of a piece of 20mm steel plate and it took all my strength hanging off a 3ft lever to shift it. The allen bolt almost gave me a black eye when it did budge. Job done though.

Clutch off now as well so crank out tomorrow. £23 EBC holding tool was well worth the money.

I can get a 0.15mm feeler gauge between the main bearing shells and the crank at both ends so it looks as though I am way outside the 0.1mm upper limit and about 5 times the usual 0.02-0.04mm tolerance. No wonder pressure was low. Crank still turns very smoothly so I reckon new shells may do it for the mains.

Small ends are definitly worn and oval (20.02 to 20.08mm measured in two axes). Kaput. Small amount of bore/piston wear as well which I think are also splash fed from the conrod oilway.

Have found a place to get replacement rods peened (thanks to John from the forum for donating these); www.Sandwell-uk.com who charge £64.40 with p&p for 2 rods. They appear to be a reputable place with much experience of automotive surface treatment. At least I will be able to hang onto higher revs occasionally with less fear of the motor throwing one.

The truth will be revealed tmrw when the crank pins are measured up.