Author Topic: Pidjones' bicentenial build (a '76 RD400)  (Read 5811 times)

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Offline tony2stroke

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #30 on: August 30, 2020, 09:36:49 AM »
You have to ask yourself is it worth the risk, or do I just splash out now and know its all done right, that goes for everything in the engine, and you def don't want to be opening it back up again in a couple of weeks, just because you scrimped to save a little money, just not worth it IMO, and could end up costing more in the long run, do it once and do it right.

Offline tony2stroke

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #31 on: August 30, 2020, 09:45:41 AM »
I would say that is good compression rate, also the fact they are both the same.

If you haven't already got one, go to tec section, download the manual and parts list, here is a link to them.

I know there are some differences between where you are in the world, but they will help a lot, also if something doesn't quite seam right in there, ask on here, the manuals are not the gospal, they all have some errors and misprints.

https://www.aircooledrdclub.com/manuals.html

Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #32 on: August 30, 2020, 12:40:34 PM »
Thanks, Tony. Have the manuals on both my tablet and laptop. The parts lists often amplify the manual by having line drawing assemblies. Seals are on order. I'll stop off after church for a 24 mm socket from Lowe's. Also adding a clutch basket holder to the tools needed list. Is a good adjustable sufficient for the 32 mm drive cog nut?
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Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #33 on: August 31, 2020, 10:02:43 PM »
Yesterday picked up a 24mm deep well impact socket to remove the crankshaft gear. Used an electric impact wrench and it came right off.

Today, balls removed from both carbs. Finally. Took four hours for the first one as the bit broke off in the ball just as it broke through (I knew better). Second one took about ten minutes. Second carb disassembled and in ultrasonic cleaner. Removed the stator and rotor. Polished the rotor slip rings with 1200 followed by 3000 grit using isopropyl as cutting fluid.Looking pretty good now. Gasket kit came in  today, but still need seals and a few other things (like the clutch tool), so I'm waiting to pull the engine the rest of the way.  Might pull heads, jugs, and pistons tomorrow. Plan to protect rods with cardboard.

Just realized that I have a 32 mm impact socket for the main drive sprocket that I had bought for use on one of the cars. Yeah!
« Last Edit: August 31, 2020, 10:14:07 PM by pidjones »
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Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #34 on: September 01, 2020, 01:37:50 AM »
Curious. Pulled left head. A .25 over piston, both piston and head spotless. .5 head gasket (might double-up when I close). The cylider looks like crap, however. Hmmm. Mic and either bore, hone, we'll see.
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Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #35 on: September 01, 2020, 01:38:56 AM »
I see why compression is down.
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Offline tony2stroke

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #36 on: September 01, 2020, 08:48:04 AM »
The part of the bore you get the compression looks pretty good, but yes O dear, may need a rebore through the rust lower down, fingers crossed you can get away with a hone.

Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #37 on: September 01, 2020, 06:40:57 PM »
Haven't had time to get anymore measurements. Did get the lump out of the frame onto a dolly. Wow! So much easier than a GoldWing! If I can get by with honing, is the three stone method best to keep everything straight? My local auto supply store has hones with fine stones for rent (basically zero cost after return).
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Offline tony2stroke

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #38 on: September 01, 2020, 07:12:59 PM »
As with everything there are different trains of thought, the expanding ones are a good way to get the cylinder out of shape, some will say use the ball version, but they can get caught in the ports, personally I think this type is the best, just for reference below, your choice mate.

https://www.ebay.co.uk/itm/cylinder-Honing-Tool-34-mm-to-60-mm-Expanding-Range-with-4-sets-of-stones/152732523507?hash=item238f915bf3:g:59wAAOSwfRdZDgdJ

Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #39 on: September 03, 2020, 10:36:37 PM »
Well, the only hones available locally was the expanding type - a pretty nice one. AND, at O'Reilly auto parts they charge your card for it, but if you bring it back within 48 hours the charge is wiped off. I picked up the tool and a set of fine stones for it today, but decided to try the mediums first, and they worked very well. Cleaned off all of the rust marks and left the 45 degree cross hatch. Wash, wash, wash and then measure again. 64.28 minimum and 64.3 maximum. What is really off is the ring gap at ~1 mm on both pistons, so rings (and many other things) are on order. Small end end play is ~.024" just under max spec. Clutch basket holder just arrived, so the clutch will come apart tomorrow and hopefully the cases. My seal set has come it, along with the special o-ring with the knot on it.

Question - if things look Okay, is it necessary to completely pull the transmission apart to split the cases?

Still stripping down the frame. It still sets on wheels but that will stay until the engine is buttoned back up.

COVID marches on here in the US, but we are learning to get along with it while not putting ourselves or others in jeopardy. One thing for out family is vacation. Every two or three years we have rented a beach house on a North Carolina island. This year we postponed to September. We will take the daughter's dog (14 year-old mixed breed) as he loves the sand (but hates the water) and youngest daughter with us, and stay isolated from others. We will be very careful as I have to oversee a motorcycle/bicycle/crafts show at our church. Only about two dozen motorcycles last year (although quality!) and expecting fifty or so this year. There was one RD350 along with HD 2strokes, Allstate (sold by Sears) and Bridgestones. The highlight was a 1929 Henderson Ace as-found. I'll show my '78 GL1000 custom, but will not compete.
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Offline tony2stroke

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #40 on: September 04, 2020, 12:06:57 PM »
Forgive me if I am trying to teach you how to suck eggs, but I feel I need to try and explain some about 2strokes to you.

Please do not take offence.

While they are very simple engines they rely on everything being in good condition, no oil, time and condensation are your enemy, judging by the bottom of the cylinders you have had condensation or water enter the bottom end, specially as no oil in the crankcases too for the gearbox.

1mm gap on the piston rings is a lot, unless you have a very good bore gauge you can't tell if the cylinder is oval or not, as you are into the engine its best you check everything now, take your cylinders to a 2stroke specialist to get them checked, rather than half checked and put it back together only to have it fail after a couple of miles, you may need a re-bore and new pistons / rings too, piston to bore clearance needs checking too or it will rattle like hell, and then fail.

I suspect the crank will also have some rust on the conrod bearings and main bearings, even if a little it will fail soon, its not like a 4stroke, although a 4stroke will still run quite well with wear on it, a 2stroke will fail fast unless well within spec, if just within spec replace or repair, its most likely that the crank will need a re-build too, because of damaged bearing due to rust, again I suggest you take that to a 2stroke specialist for checking too.

I would suspect that all the bearings will need replacing and all the oil seals in the engine, as the oil seals can go hard and not seal anymore.

You have gone this far, its wise to make sure now that everything is correct, or you "will" regret it when you hit the power band and it goes bang, you will then have to do all this again, and could cause irreparable damage, leaving you needing another crank re-build ( they can only be re-built 3 times max) and another set of cylinders.

If a ring snaps it can damage piston and bits then go down into engine and destroys the crank bearings, as well as damaging the bores, sometimes beyond repair.

Sorry to be the bringer of doom, but I feel you need to know all this before you go any further.

I write all this because of the questions, it would seam you are not that familiar with 2stroke engines.

I wish you good luck with it, and I hope there is not any rust or too much damage anywhere.

Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #41 on: September 04, 2020, 12:54:46 PM »
Thanks for the knowledge, Tony. No, I have no service experience with 2 strokes beyond a simple piston swap on a Penton (Sachs) 125 back in the '70's (well, I guess 8 1/8" piston diesel doesn't count). I do have some 4 stroke experience on CB750 dohc and GL1000 Hondas which seem very resilient.

The piston-cylinder fit is (within my feeler limit) ~.0015". The .002" feeler will not go. I will check Tuesday to see if one of our club members has a good cylinder gauge as I have been doing multiple snap-gauge readings (very carefully) measured with both digital caliper and vernier micrometer. I am sure the club has references to local 2 stroke experts, also - and will consult. The pistons still measure spot-on 64.25 mm. The pins are tight in the pin bore.

All oil seals are now on-hand along with the clutch cage holding tool. BTW, one hour's time was invested in pealing the adhesive vacuum-seal clear wrap that EBC attaches their tool to the cardboard with. I'm sure all here have a clutch basket holding tool, but if one needs purchased please factor the stupid waste of time removing the packaging from EBC's product into your buying decision. I would have paid 5% more to not have that hassle.

The inside of the piston crowns do show carbonized oil, so they are definitely used. The 2nd ring on the right piston was stuck and I had to soak with penetrant then worry it to remove without breaking. I will wait until new rings arrive before cutting one to make a groove scraper.

It appears that US supplies of most new parts has dried up, and Yambits is one of the few sources that I find, so much is coming from them. Happily, shipping has so far been just as fast from the UK as North America.
« Last Edit: September 04, 2020, 01:00:39 PM by pidjones »
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Offline tony2stroke

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #42 on: September 04, 2020, 02:04:37 PM »
Piston clearance is OK at that, but if you used a single .0015 feeler it most likely wont be flexible enough to give a accurate reading.

Please tell me you did not buy Shambits seals, they are known to fail fast, and their bearings are no better, cheap and useless, a quick search on here will tell you that mate.

Fowlers are the place to get genuine seals and bearings, not cheap but worth the extra money, they last for years.

Or you can just get the number off the bearings and buy Genuine Koyo or other well known brand, NTN as Honda use too are very good IMO.

Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #43 on: September 04, 2020, 02:49:23 PM »
I bought my seals from Mikes XS.
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Offline pidjones

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Re: Pidjones' bicentenial build (a '76 RD400)
« Reply #44 on: September 05, 2020, 02:06:05 AM »
Stripping down the engine. Had to run for a socket for the clutch bolt. Ready to pull the shift cam stopper bolt, but decided it would be best to clean the bottom of the engine of ~1/4" grime first. So, it is setting on its left side with the right cover back on and foaming bathroom cleaner soaking. The socket run and cleaning slowed me down, but there is no rush. Also boxed up some frame parts and took them and the rolling chassis back out to the shed leaving more room for engine work.

I've put in a Facebook Message to one of our club members local that has done a few 2 strokes to see if he knows of a 2 stroke mechanic locally. There is a small engine shop just a couple miles away that appears to be dedicated to lawn equipment, but I thought of asking to see if he has a good bore gauge.
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