Making one engine out of two

[RichV]

I need some help/advice.

I have two engines of roughly equal mileage. One engine was on a flooded bike and has two rusted cylinders and matching trashed pistons. The other leaks but has near perfect cylinders.

My goal is to take good internal parts from the one that leaks and replace the ones in the flooded engine. That way the engine serial number will match the frame and that is important to me.

So I completely disassembled the flooded engine and took the cylinders off the leaking one. I will take the flooded engines case and fill it with all of the leaking engines parts.

I plan to still used the flooded engine's case, cams, valves and head (there's a broken fin on the leaking engine'd head) and the leaking engine's cylinders, crankshaft, rods, pistons and transmission (all internal parts that are working).

So here is my question. Which crankshaft bearings should I use? Should I still match the crankshaft and rods to the original engine cases and reuse the matching bearings? Should I just get new bearings? What bearings should I get and where can I find them?

Thanks again for the help and advice.

Please remember that I'm good at this but I have never dissembled an engine to this level before. Also, I'm replacing all gaskets and seals.

[TopCatGr58]

Hey Rich,

Due to production variances in the cases, I would highly recommend keeping the crank/bearings matched to the crankcase they were originally in. I don't know if you have ALREADY split either or both engine cases but you can SWAP just the pistons from the Leaking engine onto the Flooded Engine crank/con rods without having to split the cases or disturb the crank/con rod bearings! The bearings are fairly hard to find as well as $$$!

I can't remember all of the details about the FLOODED bike/engine?? Do you mean it was in a Rain/Water FLOOD, and WATER/?Salt water got into the engine/crank area???? With the oil filler cap on tight, the water could have slipped down past the piston rings and into the crankcase, but unless the engine was actually turned or run, the water shouldn't have gotten inbetween the bearings and crank/case/conrods????

Tod will probably say you should split the cases, inspect the crank/con rods, use plastigauge to determine if they are still in spec or not!? Without knowing if there is water/rust damage down in the crankcase area and not just the Pistons/Rings/Cylinders of the Flooded engine, I can't suggest or recommend trying to use the Leaking engine's crank/rod/bearings?

I will tell you that I had ~50k mile on my 81 when I did my 1179cc top end rebuild, just put the new pistons onto the existing crank/con rods...the kit did come with new wrist pins, have put another ~15K miles on it so far without any sign of problems....no knocking or such! The OEM crank/con was designed to last 100K or more miles...the pistons/rings will wear out much faster than the bearings!!

T.C.

[RichV]

Here are the details of the two bikes:

Flooded: Found in someone's back yard off the Chickahominy river. It sat for eight years and the tires sank into the ground. The area flooded during a hurricane and the bike saw water up to half way on the Ignition Advance cover (sitting on side stand). When I drained the oil, there was a small amount of fresh water present. I tore the engine down and none of the parts showed any rust or excessive wear. The cylinders and pistons, however, were trash. I have a clean title on this bike.

Leaking: I got this bike from a father wanting to get ride of his son's "crappy bike". It sat for only 6 months and after rebuilding the carbs I got it to run and blow oil out of the seals and some gaskets. Tear-down thus far shows an engine that was abused a bit more (bad oil?) but has pristine pistons and cylinders. The problem is that I don't have a clean title, only paperwork for the sale. A title search shows that it's not stolen.

My current plan was to put the parts on the leaking bike that were working on the flooded bike. I've done everything but the engine which is my current project.

The bearings, crankshaft and rods all look good on the flooded bike. The leaking bike cams had some scrape marks on the bearings so I don't have a good feeling about the crankshaft.

So I will use the flooded engine's case, crank rods, head, cams along with other parts. I will use the leaking engine's external parts and the cylinders and pistons. I will replace other parts (trans, chain, valves) as needed.

I may also plastigauge the bearings just to make sure.

I currently do not plan to replace any bearings or re-glaze the engine cylinders.

[mack]

rebuild

There are a series of numbers on the crank shafts and on the underside of the upper case at the upper motor mounts. These codes will tell you what the main and big end bearings are supposed to be. Hopefull both motors have the same codes so it should be a one for one swap. However, as TC said, plastiguage will be your best friend.

[RichV]

I could not find anything near the upper mount but I did find the numbers:

2H700 Y-2 on one and
2H700 Y-21 on the other

Both were inside the case halfs near the back.

On the crankshaft I found the numbers:

22222 and
2121

They were next to each other and I guess the first is the crank and the second is the rods. I don't know what they mean.

I've decided to use the leaking engine's head even with the fin broken off. It's the front right fin on the bottom and its just the tip of the fin tip broken off a quarter inch. It's not that bad.

The flooded engine has messed up exhaust valves that I just don't want to deal with. If I go that route, it will be next year before I finish.

[mack]

numbers

the numbers won't mean anything until you get a look at the left side of your crank shaft. They have numbers as well in series of 5 and 4 numbers corresponding to the journals. You subtract the crank numbers from the case numbers and enter a table and that will give you a colour code. But that's not important right now. What I was suggesting is that the upper case numbers might be the same on both engines.
If your swapping parts, then you'll have to split the cases in both anyway. When you do, check out the numbers on the cranks. Subtract the two and you can enter a colour chart listed in all manuals and that reveils a bearing shell colour. Then you will know what can be easily swapped. No matter what, even if they are interchangeable, you'll need plastiguage to ensure they are with in limits.
3phase had a post in 2009 when he was doing "columbo" that had thickness tolerances for each colour, he gleaned from the UK site.
After you prep the surfaces and do the guage, you may have to drop or go up a colour to hit the right tolerence. Why they chose colours instead of numbers is ......... well, a mistery unless it was to bridge a language and math gap between continents.
Post again when you figure out what shells you need. I may be able to help.

[RichV]

Now it's been three months and I tabled this until today. I'm just about to put the case back together and I need to order bearings. I've determined under closer inspection that the older bearings are worn too much.

So my original question still holds. What size to I use?

Well, I've been all over the net going to many sites on Yamaha products and I "think" I have the answers.

The stamped numbers on the crankshaft are "22222" meaning all are the same.

On the case, the ONLY stamped numbers I found were "6S 90" located on both the top and exterior bottom halves of the case by the back mount (see photo below).

As near as I can tell Yamaha will use only one number if they are all the same and "6" is in the normal range. Using this logic, and the necessary math, the bearing size is 6-2-1=3 which is brown on the color scale.

Knowing this, I should get the BLACK bearings to account for wear and Plastigage them when I install. Does this sound good?

I found a set of black bearings Here. It they are correct. Price seems okay.

Here are the photos:

[DiverRay]

That link is for A SINGLE BEARING! You need 10 bearings for the engine. I would just go with the browns, as they should work well for about 75K miles or more. A slightly looser bearing on the mains will drop the oil pressure slightly, but the pump should have no problem keeping up with demand. I do not know what I need for my engine, but I do have a box with a few bearings left in it. You could try member Andreas and see if he has some "good" bearings.

[RichV]

I actually only need one bearing pair. I have one that has too much wear. That said, I'm thinking of just using the set (with crank and rods) from the other engine if they're okay and the clearances workout.

[DiverRay]

Let me know the color, and I'll see if I have a pair available.

[mack]

Calc's

Maybe this will help Rich. Here is the location of the numbers you need to do the calc's for you main shells.


Here is are the calc's for mine as an example.

[RichV]

Now this was very helpful. It also explains why I couldn't find them. The stamps are so light that all I see is a series of "+" which I can only assume are "44444".

Below is a photo of my case and you can (or can't) see the stamps.

Since my crank was "22222" I can assume that I need "2" bearings (Brown). Does this sound correct?

Thanks for showing me the location using the 1000 word equivalent.

[mack]

Rich

2's would be black. Since the numbers on your case have been polished off for the most part, I really think you need to plasti guage the crank mains. It's very easy to do and will give you all the info you need to select the right shells. I'd put the originals back in from either case/crank and do the guage thing, then work off those results. That will tell you if you need to go up or down a colour. Between Ray and I we should have the colours you'll need. It's tough seeing the colours well on the used shells but from the numbers you've shown so far I believe you probably have blacks in there.

[RichV]

I think all black is the way to go. I can't see any color markings on the edges except on one which might be black.

I'm going to tear down the other engine and look at it's bearings.

I used a micrometer to get a general idea of the bearing thickness. The all were around .058" thickness.

If I use the bearings out of the other engine (which is also marked with all 4s on the case), I will probably use it's crank and rods as well

[DiverRay]

Try to keep the rod bearings WITH the rods they came out of! It may make the engine run a little better, as they will have already conformed to the rods. let us know what you find when you gauge them.