Linkin's FZR250 3LN6

Well I've been reading this and going off what it says it's most likely a rod bearing as the noise is not there when the engine starts, and oil pressure is fine.

I don't really mind having to change them... it means I can also change the pistons, piston pins, rings, stem seals, cam chain if necessary & clean up the valves, clean the head etc.

I just hope its not a main crankshaft bearing... touch wood...

 

Well we have moved house and I can start pulling the motor down now.

Still waiting for the remaining fairing pieces to arrive.

My TAFE course also finishes at the end of November so will have more time to power through the final stages of this project!

 

Straight to the action, no messing about.



An interesting tidbit I thought I'd add. Looking at the exhaust valves through the exhaust port, you can see how well that cylinder was running. Like reading spark plugs. #1 was lean, #2 and #3 were good, #4 was rich.









Pulled the head off and all the valves were straight. Have not leak tested yet but suspect they are just like the other engine... leaking all over. However I've never seen camshafts with this sort of pattern on them. Can anyone shed light on that?



Haven't got a pic of the bores but they look OK. Will get them cleaned up, measured, and honed when I can.

So the noise was indeed a big end bearing. No. 3 has lots of slop

 

Whadda you mean!? That's a protective layer of road grime I'll have you know!!

 

I haven't taken No. 3 conrod off yet, but the good news is that all 3LN engines use the same part number for the crankshaft. So I can either use a good spare or price a brand new one

 

Well I just pulled off No. 2 and No 3 conrods. At first glance it is not as bad was I was expected. Though I might not be trained enough to make that call. Here is No. 3 crank and conrod...







Pretty obvious scoring mark towards the centre there on the bearings that can be felt with the hand. But what caused it? Debris getting trapped during installation? Long periods without oil or filter changes?

The top half bearing also appears to have been squished out from the sides. The bottom one has a little bit, but it appears to have followed on from the top half.





Here is No. 2 crank and conrod/bearings





At TAFE there is a nice big chart of conrod bearing failure types and what causes them. Will take them in and compare notes, and maybe ask the engine guys there.

Otherwise any opinions or advice is welcome... such as whether I can get away without regrinding the crank and just replacing all the conrod bearings (plus No. 3 conrod with a spare - I wouldn't trust it after bearing failure)

 

Which ones? Or all of them?

Here is the inside of No. 2 and 3 rods & bearings, respectively. I wiped them clean before taking photos. Smelled very burnt and a bit of carbon came off... Probably goes back to how the oil was about 500ml's of black watery crap when we got it...





And a closer look at the top half of No. 3 bearing... squished. Both halves had the locking tabs broken



One of the bolts for No. 3 is very stiff and doesn't come in or out easily... compared to No. 2 where it basically falls apart when you undo the bolts.

 

Can you explain exactly how to use plastigauge, I've never even heard if it before now.

 

Well I pulled the last 2 rods off and I would have to agree... oil maintenance was severely neglected. I guess the fill of Delo was just delaying the inevitable for the other 3 sets of bearings. No. 4 bearing was about to let go... went to pull it out and the locating tab just about broke off. Wasn't far behind No. 3

Ran my fingers around the conrod journal areas on the crank... 1, 2, and 4 were all smooth and felt OK. No. 3... yeah, nah. No chance.

My current plan of attack is to get the crank out and chuck it over my shoulder... and get another crank from one of the many spare engines at the fizzer factory, maybe the rods too, and if it measures up OK, put new standard bearings in (and properly)

 

Well searching the old google finds that the diameter of standard con rod bearings is about 27mm or just under, due to wear on the old ones. The chinese ones list the same spec.

So here stands my plan of attack... comments or recommendations welcome

Crank & rods from spare engine, inspected & measured
New main bearings and conrod bearings from aliexpress
New pistons, rings and little end bearings + circlips from aliexpress (and comparing weights/dimensions as recommended)
Clean up & hone the bores
New EBC SRK34 Clutch kit

While the cases are apart & waiting for parts, replace whatever else needs doing eg roller bearings, clutch thrust washer, etc.

It is getting closer to Christmas so that means the postman will be busy, hope to get all the parts before the really busy period in December.