Engine Rebuild - any advice?

This is advice for low end, hobby rebuilds:
You can compare the bore between the good cylinders with the bad one by sliding in a compression ring and measuring the gap between the ring ends with a feeler gage. Set the ring at different depths of the cylinders and compare.
You can hone that bad cylinder with a rented hone and measure it again before you decide to buy new rings. But I think it's going to be too badly scored to use as is, however you can have it re-bored.
Because this is your bike and hobby, low end is OK.
By the same token, feel free to be impractical and spend a little money, claim it on your income tax as education and retraining.
Bill

 

I with BigFitz, he says it all.
Proto has darn good advice too, though you might want to check with your tax agent before you claim that tax deduction unless you can show you are pursuing a career as a mechanic.
Good luck on that motor.

 

Alright, I'm soaking that cylinder in kroil (There really isn't much that I can hurt at this point doing that, right?) and I will pull off the bottom half of the head in the next couple of days assuming I can find a larger space heater.

Looks like I have some reading ahead of me. One more question before I start trying to figure all of this out from some books. If I re-bore, what other changes will I have to make? Will I have to re-jet the carbs? Adjust the exhaust? Get a radiator? Change the timing?

I'm pretty gung-ho about all of this (I'm paying for this garage every month, I want to get as much out of it as possible) but I am trying to figure out how much it will cost and how many favors I will have to call in.

 

First off: RE: Space heater: I heat my garage with an indoor-safe, wall-mounted propane heater running off a standard bottle like a bar-b-que. (It doesn't have to be mounted it could stand up too.)
TOASTY. It's 14*F outside, and I'm in the garage right now on the laptop and its toasty, and the heats only been on an hour or so.

Re-boring won't cause you to have to re-jet or do any of those other things; the carbs will need to be re-ADJUSTED when you put it back together, re-bore or not.

Cost will depend on what you find. If that cylinder is destroyed, actually reboring would mean finding oversize pistons and now you're talking big money. If honing won't clean it up, I'd be on eBay looking for a parted out cylinder bank with pistons that honing WOULD clean up, and you could just buy rings.

The problem with these old bikes is that the law of diminishing returns kicks in REAL quick. You can EASILY spend $300, $400, $600 OR MORE completely rebuilding one of these motors, if you can even FIND the parts. You'd have to drop a good $500 or so for a set of aftermarket 10-over pistons, since the real thing is most likely unobtanium. At some point it makes more sense to go find a low-mileage motor with decent compression for $200 or less, unless you're fanatic about the frame and engine numbers matching as in a full on resto.

Let's get that cylinder cleaned up (after you pull the jugs) first.

 

Would a SECA engine fit on my Maxim frame?
http://cgi.ebay.com/ebaymotors/Yamaha-1 ... ccessories

 

There was a guy on the forum who picked up SECA engine off CL for $20 (i saw it but didn't jump on it) listed at $50 in MA. Search "aluminum boat anchor" on the forum (it was a steal because it had more pieces). Engines can be hard to get rid of because they cost so much to ship, so you kinda lucked out that this is in your area. Also, if you search on CL, keep in mind that an engine may not have the words SECA or MAXIM or XJ attached, because the bike/frame may be long gone. The one I mentioned was just listed as "Yamaha 750cc" and was supposed to be for a go cart project. I called the guy and asked about the YICS.

Starter motor is still on there, so at the very least bring a battery and compression test that thing (someone may have advice on how to do that off the bike), maybe you could make sale dependend on compression test and talk him down a bit.

 

A 750 isn't a PURE bolt-on to the 650 frame, there is a difference in the shifter linkage and a couple other minor fabs you need to do. Do a forum search, that one comes up all the time. Search on 750 in a 650 and see what you get.

I wouldn't even CONSIDER buying that motor without a compression test; you don't want another example of what you have already.

$200 is a bit steep considering the "lack of pedigree."

 

Update:I have gotten the bottom half of the top of the engine (what is the right terminology for this part?) off.


I have also taken the pistons off:


Sooo, the inside of the cylinder doesn't look as bad as I originally thought. From what I have read, I think that it can be honed without being re-bored (will get some better pictures up here soon and will get some more opinions).

As usual, I have some questions and - per usual - I have numbered them:
1. There was a significant amount of rust (and road grime, and sandy-looking stuff) trapped in crevices of all of these parts. Now, all of that sandy grossness is stuck to the sides of cylinders, pistons, and perhaps a bit has dropped in to the lower part (again, help me with some terminology here). What is the best way to clean this? If I wipe it with a rag, I am nervous it will scratch... unless this is OK. Compressed air? Is there some chemical I could/should dip these parts in?

2. The studs that the parts of the engine fit on and slide down are sticking straight up. I would like to turn the engine over in order to get the oil pan off (also, to try to shake out any dirt that fell in there). How do I get these studs out?

3. Do I need to buy a new cylinder? The only part of the cylinder that looks bad is the top. The sides are still pretty.

4. What is my next step? Should I focus on the head/cylinder (it will be at least a month until I have enough cash to get the cylinders honed)? Ultimately, I would like to take apart everything that I possibly can, clean it all up, and put it back together... should I start taking off side panels and sanding them?

5. Lastly, but still in the vein of cleaning, a friend told me about a service where they will dip an entire engine into a vat of some sort of chemical and then flush it all out and it will clean everything. Is this something that anyone here has experience with?

OI! A lot, I know. I can't thank you all enough, though. Your help with all of this stuff has been invaluable.

 

Flush out the motor with cheap engine oil.
You shouldn't need to drop the pan.
Have the cylinders & head soda blasted.
You have to test the bores for size & roundness, you can do this by putting a piston ring (on top of a piston to keep it square) & measure the gap between the ends of the ring. but if you are not sure, have this done by a pro', you can then tell if it needs reboring or honing or throwing.
Keep up the good work.

 

1. I would blow all the crud off with compressed air (compressors are worth every penny spent IMHO). Shoot everything in sight with brake/carb cleaner. I would drop the pan as a matter of course given the condition of the upper end. You need to ensure it isn't rusted up down south as well.
2. Throw the cylinders and head back in place to flip the engine if you can't make matching holes in a 2X6 plank.
3. Don't know. I'd need to see better pictures of the cylinder before I could even hazard a guess.
4. You should have the engine parts soda blasted. Money well spent.
5. Hot tanking aluminum is not a good idea. You are best served disassembling the motor and having it all soda blasted after you clean it out and reassemble it. Best bet is using a selection of bore brushes and hot soapy water (liquid dish detergent works) followed by WD40 to prevent rust.
Good luck.

 

Hey everyone. Miss me? Work has picked up around the holidays so I haven't done much since last writing. After a closer (and cleaner) inspection of the trouble cylinder and the piston I think that I am going to be able to use it! Which is pretty awesome. Obviously, still going to get it checked by a shop, but taking my time degreasing everything before I bring it in.



Other awesome news - $75 gift card to Sears for Christmas (thanks Mom!)

1. So, first thing's first - I want to take off the oil pan and all side covers (clutch, gearbox). Remember, Wiz, this is more an exploration for my own edification than a get-it-up-and-running project (although getting it up and running is certainly on the docket). Besides, I want to get it SUPER clean and nice looking.



I have taken all the bolts out of these covers, but can't seem to convince them to come off. TRIED: rubber mallet, wood block with hammer, a bit of kroil, propane torch. Won't even budge.

2. Robert's preceding post indicates that I should get the engine soda blasted as one piece. I was planning on bringing individual pieces in and getting them done (or doing them myself). That way, I can make sure to get inside the cylinders, etc. Thoughts?

3. As it gets colder, I am wondering about my garage. Should I worry about metal parts (like the pistons or the valve cover) getting that cold while out of the engine? Will they warp at all?

4. As a $$ saver, I'm thinking of making some of my own gaskets. I want to do valve cover, clutch, and gearbox. A friend of mine suggested that I hold the gasket paper up to the part and just tap around the edge so the machined edge of the metal will dig in. Anyone else have any tips?

 

With the drain pan, I've marked the oil level sender with a circle and '+'. You'll need to remove that first (it will leverage out, it has an o-ring so it will be tight).
Also I've indicated where you still have bolts (you may have already removed these, but just in case).

You may have to carefully leverage around the edges where appropriate to gently force the pan away from the crankcase.

1st time I've tried these attachments, hope they worked.

And the gasket Idea sounds good to me. use a round holepunch when making the holes for the fasteners to pass through the gasket so you don't rip it.

 

Sorry, here are those images.

 

Don't worry about your metal parts in the cold, private parts are a different matter. :lol:
Don't be blasting inside the bores.

 

Champ - thanks for the heads up. I have removed the sensor and all of those bolts. Still doesn't want to budge. I'm hesitant to push anything in there for fear of scoring the gasket edge. Your drain pan looks great.

Wiz - seriously. My privates are freezing.
Thanks for the tip on the bores. Is there anything I need to do to clean them up before honing? The one cylinder has rust on it and I thought I was supposed to soda blast to figure out if it's worth it to hone. That said, if I don't have to do that, I might be able to just clean it up with brake cleaner and not need to hone at all.

 

That #4 cylinder that had the water in it would be the one to really inspect. Once cleaned and lightly honed, Hopefully you don't have alot of corrosion/erosion in that one.

 

Bump. Any advice on getting this oil pan off?

 

I did it!



Probably not the BEST way to do it, but I ended up CAREFULLY grabbing a hold with some vice grips (I know, it's aluminum, I did a lot of cringing as well) and pulling it straight off.

Inside the engine:


Now I get to figure out what all of this stuff is. What are the cranks near the top of the picture and what is the name of the filter thing that looks like a flying saucer?

 

Near the top of the picture is you gears. the flying saucer thing is the filter for your oil pump.

 

Good job getting that pan away. If you put enough elbow into it, you should be able to remove the three bolts holding the back plate on so you can get in there and clean it up like new.