27 J engine strip

[Martin Pettingell]

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This thread follows on from the one yesterday asking for help to get the manifold off. Thanks for the tips. I lifted a cylinders just a shade and it came free.

I have also now removed the cylinders and exposed the pistons. The rods look like originals to me but the pistons clearly are not. See the picture.

I have only worked on flatheads before - a 45 and a UL - and these pistons look similar to UL to my eye but i am no expert. Any body recognise them and know whether they would be suitable to re use - assuming they clean up ok.

The front piston has a number still on its head - 020 - and also a circle made by the timing plug by the look of it. See picture. Nothing i can see on the rear.

The plugs were original but there was little or nothing left of the gasket / washer when i took it out which may be why it was brushing the top of the piston.

I am hoping that the mark is just in the carbon and hasnt got into the metal too much,

Probably my biggest issue is the rear baffle - half of which is missing entirely. See picture .

I am thinking that this will fundementally effect the oil circulation if not repaired. Is that correct ?

I am in the UK so will be looking for somebody who may be able to repair the baffle - any suggestions would be very welcome

The front baffle has had bit chewed out of one side but not too severe.

The crankcase will obviously have to be stripped to repair the baffle and when its apart i may as well get the bottom end re built but currently the front rod seems free of movement. The rear rod has a little side to side play in it which is a concern


Some good news - although the cyclinders have fins missing and need attention the bores look ok - smooth and no obvious scoring. I havent measured them yet but i am hoping that they can just be tidied up and reused.

Thanks

Martin

[harleytoprock]

If you are planning to use pistons with modern oil control rings, you can cut out all remaining baffles as they won't be needed.

[Steve Slocombe]

Dear Martin, those look like later pistons with oil rings and the 1932 style piston pin clips. Check underneath and see if you have the steel strut holding the skirts together, in which case they are the 1938 style flathead pistons. The 020 means twenty thou oversize, so plenty of meat left on the cylinders. An imperfect baffle repair risks dropping pieces of aluminium into the engine, and you know the engine has covered many miles as it is now. I'd tend to leave the baffles alone. The forked rod is on the front on the JD so often does not show much side play. The plain rear rod can take up to about 0.1 inch side play and still be usable. Clean most of the oil off the crankpin rollers with a suitable solvent and check again. You don't want any noticeable vertical movement. Not splitting the flywheels saves a bunch of money, so evaluate carefully. You could almost put the bike back together for this season and then work on it in the winter...

[Jerry Wieland]

If it was my engine I would not remove any part of the baffle. My next JD engine is going to have a full baffles and a 3 piece oil control ring in the rear hole and in the front hole I am going to run a 3 piece oil ring and leave the expander out. You just about cannot stop the rear cylinder from over oiling and it is real easy to under oil the front cylinder.

Jerry

[harleytoprock]

Jerry, What makes you think the rear cylinder is over oiling? Thanks

[Steve Slocombe]

On the JDs and VLs the flywheels rotate clockwise when seen from the right side of the bike, so splash oil preferentially into the rear cylinder. We see various baffle arrangements on the JD, VL, DL, RL as the designers think of ways to get oil mist to the front cylinder.

[Martin Pettingell]

Thanks guys - plenty to think on here.
The carbon on the front piston just wiped away and it still looks pretty good. The rear piston has a much thicker and harder layer of carbon. It took a lot wiping over with cloth soaked in paraffin to remove most of it and it has still not cleaned up as well as the front.
Both pistons have the same circular mark in the middle - so maybe they started out like that. Both show 020. I cannot find any numbers on the inside to help ID them.
Back at the day job now so further work will have to await the weekend.
Martin

[Steve Swan]

I'm really enjoying immensely reading this thread. Thanks guys. i follow this and other boards daily for any JD gems of information.

i'm restoring a 27JD. Both my cylinders were able to be taken to .005 o.s., so i feel fortunate there. Fitted with Venolia's with a dome.

Just my inexperienced observation on things JD (i'm just trying to learn as much as i can) but it seems there are somewhat differing opinions on to keep baffles v.s. not to keep baffles, install oil ring v.s. not, remove expander on front oil ring.

Again, i'm just trying to learn as much as i can and understand. For the sake of not using someone's name without their permission, the man who did my boring work and recommended using the Venolia's said to run oil rings with their expanders front and rear. my baffles are intact. i will not be Cannonballing my JD, will be ridden at most a few hundred miles a year, no more than 50 miles at a time.

What i am taking away reading these different opinions, how the engine is sued seems to produce differing opinions.

Like i said, i'm trying to learn.

[Jerry Wieland]

Jerry, What makes you think the rear cylinder is over oiling? Thanks

Because every one I have ever taken apart and every one I have ever seen apart is sloppy wet. Ever seen a rear piston scored - I never have - its always the back side of the front. The baffles are there (in my opinion) to get oil past the rear hole and into the front hole. Jerry

[Steve Swan]

I understand how the rear baffle is intended to get oil to front. Does front baffle not impede adequate oiling ?

(I understand Jerry plans to run baffles front and rear; no oil ring expander in front.)

[harleytoprock]

There are different theories about case baffles. On my '27 JD I am running Eastern flathead pistons with oil control rings and no case baffles. I get no oil burning exhaust smoke or any over heating. I ride it quite hard and have been clocked at 75mph. I ride for hours of non stop at a time. It's been running on the road for the last 6 years. The proof is in the pudding. Harley has been, for many years, running oil control rings and no baffles, with no problems in V-twin motors. There is no reason to not update a JD or any HD motor to modern practices.

[Steve Swan]

There are different theories about case baffles. On my '27 JD I am running Eastern flathead pistons with oil control rings and no case baffles. I get no oil burning exhaust smoke or any over heating. I ride it quite hard and have been clocked at 75mph. I ride for hours of non stop at a time. It's been running on the road for the last 6 years. The proof is in the pudding. Harley has been, for many years, running oil control rings and no baffles, with no problems in V-twin motors. There is no reason to not update a JD or any HD motor to modern practices.

What is your piston, cylinder wall clearance ?

[harleytoprock]

Steve, The pistons are steel strutted. I had the sides coated with the magic black stuff. The clearance is .0035

[Steve Swan]

What's the magic black stuff ?

My cases have their baffles and I'm using domed Venolia's. I'd appreciate hearing thoughts on this combination. .0045 wall clearance.

[harleytoprock]

I had this company apply their PC-9 to the piston skirts.
http://swaintech.com/race-coatings/m...s-price-sheet/