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Post by shaunthe2nd on Feb 14, 2014 19:26:13 GMT 1
My 250LC 4L1 refurb and rebuild is progressing slowly and i'm getting a bit more confident taking things on. Today I stripped the head down,was a bit worried since 30 years since I did anything like this, but seemed to go ok (apart from not realising I had to drain coolant from both sides - i thought that removing just one drain plug would suffice lol). I did this for 2 reasons, first to get them off to clean them up and repaint. Second to have a look at the top end to get some idea if any engine related problems. When I bought the bike it started easily, and revved well, no obvious rattles etc, but I never rode it prior to strip down. I'm no expert, but wiggling the pistons doesn't seem to show and obvious wear on the big or little end. The pistons and barrels look ok, but I wouldn't mind the view of the more experienced collective. The following pics I took today. Can anyone spot anything I should be concerned about? Thanks in advance, Shaun       |
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Post by spooch63 on Feb 14, 2014 23:07:13 GMT 1
Nothing to worry about there, piston crowns could do with a clean but other than that all looks good, good luck with the rebuild
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Post by steve h on Feb 14, 2014 23:35:09 GMT 1
Looks pretty good, no previous damage. Needs a new stator sleeve/grommet  |
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Post by marsbar350 on Feb 15, 2014 0:00:12 GMT 1
as above shaun.everything looks good ignore martin(headcoats)  if it aint f**ked leave it alone norbo does the grommet thingys £6 |
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Post by twostrokebrit on Feb 15, 2014 0:03:17 GMT 1
whats the mileage on the bike? and is it on std bore?.
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Post by steeley on Feb 15, 2014 8:19:58 GMT 1
looks ok ,clean the piston crowns and fit new rings.ports look like they have sharp edges from a rebore , if so chamfer them up.
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Post by dusty350 on Feb 15, 2014 10:16:26 GMT 1
Hi Shaun,
It all looks in good condition. Nice to see the domes in the head have no pitting (detonation) damage. I would clean the top of the pistons too, and you will see if it's been rebored , and if so, by how much. I would take the pistons off to do this, and get a closer look at them to see what make they are for the rings if you change them. New little ends and circlips too whilst you are doing it. Genuine Yam gaskets if it was me. Starts adding up a bit, but worth it.
Dusty
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Post by muttsnuts on Feb 15, 2014 10:49:37 GMT 1
Shaun, all looks good, if you get stuck give me a shout and I'll pop across
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Post by shaunthe2nd on Feb 15, 2014 11:29:57 GMT 1
Shaun, all looks good, if you get stuck give me a shout and I'll pop across Thanks Dave, hope it doesn't come to that, but you never know, cheers. Hope your project is coming along, if you get stuck give me a shout......!!  |
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Post by shaunthe2nd on Feb 15, 2014 11:32:09 GMT 1
Thanks for all your comments and advice.
I think I will take the pistons off to clean them up, but don't think I'll go as far as splitting the crank.
Then again i said i wouldn't end up cleaning and polishing old washers....
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Post by AndyYam on Feb 15, 2014 12:36:57 GMT 1
I'm nowhere near as experienced as most of these guys but will still offer up my opinions. Looks like the rings have been sealing nicely. No signs of any serious blow. I personally would have cleaned around the bottom end before taking the barrels off. Can see some of that dirt and bits of corrosion from the cylinder studs has gone into the crank. To me this would mean splitting the cases to clean but maybe im just over cautious and im sure others would have different views. Don't forget to pack the cranks with clean rag if you do take the pistons off. Nothing worse than dropping those cirlips into the crank and so easily done! Been there! I would also "skim" that head. Using wet and dry on a sheet of glass in a figure of 8 motion and keep replacing the wet and dry with finer and finer paper. Just because it looks like it would be a right pig to remove all that old gasket residue with a scraper. Yeah as said before its nice to seem some nice smooth non pitted combustion chambers. I personally like to polish these up as I do with the piston crowns. Just to prevent cabon build up in the future....and it looks shiny =/  I'm sure you'll be checking jetting etc once you rebuild and others might disagree but from the top of the pistons does it look like its running a little hot? Hope I dont come across as teaching you to suck eggs. You say it was 30 years ago you last did this. Well 30 years ago I was 7 years away from being born so im a relative newbie but like to try and help! |
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Post by dusty350 on Feb 15, 2014 13:18:57 GMT 1
Hi All valid points Andy. I use one of those soft sanding pads to clean up heads and pistons. Doesn't take long to get them looking nice and clean;   And before and after pistons;  Dusty |
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Post by shaunthe2nd on Feb 15, 2014 13:22:49 GMT 1
Andy, you certainly not teaching me to suck eggs, i probably did all this without thinking all those years ago, but age and time has taken its toll so i appreciate the tips and advice. Some good pointers you have given me, thanks.
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Post by shaunthe2nd on Feb 15, 2014 13:24:20 GMT 1
Hey they look good Dusty, you have inspired me to do the same with mine. Thanks.
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Post by dusty350 on Feb 15, 2014 13:35:16 GMT 1
Hi Shaun, The weather being crap means it's a great time to do these sort of jobs. Well worth the extra effort. Enjoy Dusty |
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Post by shaunthe2nd on Feb 15, 2014 19:45:42 GMT 1
whats the mileage on the bike? and is it on std bore?. The bike has only done 13,500 miles. Just taken the pistons off and cleaned them up, see picture. Inspired by Dusty! They are stamped with a 'L' on top of both, does this indicate bore size? I can take barrels to work on Mondat and get them measured, but does anyone know what the 'L' means?  |
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Post by twostrokebrit on Feb 16, 2014 19:44:29 GMT 1
the size will be on the crown and first over would be 0.5 or .5 (1/2 mm or .020thou)
second over would be 1.0 (1mm over or 0.04 thou) and so on.
i think std bore is 64.0 mm and a cheap set of calipers will show what size bore you are on.
i would think the L would be for left and right but i didnt think they were handed so i am a bit confused about that.
you measure the piston for wear i think the haynes manual says 5mm from the piston base @ 90 degrees to the wrist pin.
mark
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Post by shaunthe2nd on Feb 17, 2014 0:33:24 GMT 1
Thanks for all comments. i will try to get pistons and bore measured tomorrow.
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Post by shaunthe2nd on Feb 18, 2014 20:10:13 GMT 1
Measured the bores and pistons today.
Bore is as near as dammit 54.0mm and pistons slightly less.
From this i'm guessing its not had a rebore and pistons etc are all original.
Looks quite sweet to me after 13,000 miles.
Nothing i've seen seems to justify cost of a rebore. A bit of a clean up and replace i'm thinking, theres plenty of other things to spend my beer tokens on!
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Post by bare on Feb 19, 2014 23:39:37 GMT 1
Looks like your pistons are in decent condition.
IF brown below the second ring ..they are definitely knackered.
Yours seemed ok there. Although there is little hope of expecting an additional 13K life out of the assembly, unless perhaps you only use it for shopping.
DO ! measure side and endplay in your rods big ends, although the smaller 250 slugs are far easier on those than a 350 is.
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Post by twostrokebrit on Feb 20, 2014 2:34:39 GMT 1
i would replace the pistons and rings and wrist pin small end brgs and retaining clips as in the first pics it shows some blow by.
a light hone to help the new rings bed in.
and your good for another 10k to 20k miles depending on how you ride it.
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