Engine restoration...

Shadowpillar · Dec 3, 2006

Okay, I'm relatively new at rebuilding engines, I know the basic part of the engine the cylinder and piston. but I have a good feeling I need to split the whole engine apart and replace some things, the poor thing sat out, in the open (with the head and cylinder removed) for 2 years, the oil had water in it when I drained it.

So, would putting in a new seals and bearings be a good idea? I dont plan on replacing the rod, it seems to be fine, but the bearings I wouldnt trust as when I would try to crank the engine to move it, it stuck until I used a lot of force to make it crank, then it would do it, but it felt somewhat sticky, which probably isnt a good sign.

So, how do I go about it? I know I'm going to need a clymer guide on the bike (DT175B) and some new bearings and seals, and a new piston connecting rod (this one is lightly oxidized and has been knocked about a few times)

Or do you guys think I even need to do this at all and just replace the piston on the bike and give it some fresh oil?

CRazy250 · Dec 3, 2006

i bet the moisture and water have toasted the bearings and bearing races, just spend the extra money and rebuild it.

Sawblade · Dec 3, 2006

If the motor set for 2 years in the elements, you need to go a head rebuild the complete motor including the crank. You may as well have the crank rebuilt as a preventive measure. You know the old saying, pay me now or pay me later. Good luck! :cool:

Shadowpillar · Dec 3, 2006

yeah, it's better to fix the underlying problems so they dont destroy other perfectly good components.

the head and cylinder arent a problem, they've been sitting inside a garage all nice and cozy, prolly just need to be cleaned and dusted. it was the bottom end that sat out, though it had *some* protection from the elementsbecause the gas tank did cover it from the rain to some extent. either way, I want to ensure that the engine will have another 10k on it afterwards. Plus, It'll give me some experience in building a 2-stroke motorcycle engine.

CRazy250 · Dec 4, 2006

clean up the piston and sand it with 800 to 1000 grit, then symachrome it. it makes it smooth and shiney and looks like new.

Shadowpillar · Dec 4, 2006

CRazy250 said:
clean up the piston and sand it with 800 to 1000 grit, then symachrome it. it makes it smooth and shiney and looks like new.

problem with that, there's a 1-inch hole in the center of the piston because the idiots who had the bike before my friend put in the wrong kind of spark plug. :)

wirefryer#85 · Dec 5, 2006

Wrong plug put a hole in the slug, that's a classic!

I bet it went like this " Oh shut up and put the plug in, they're all the same anyway. Okay, fire it up! Whats that knocking noise?" :ohmy:

Definitely want to split the cases to make sure there is no pieces of piston floating around waiting to take out a bearing or two.

Luck!

Tim

Shadowpillar · Dec 7, 2006

nah, the piston hole looks completely vaporized, not knocked out.

my worry is bird stuff and leaves in the crank case.

Ol'89r · Dec 7, 2006

Shadowpillar said:
nah, the piston hole looks completely vaporized, not knocked out.
my worry is bird stuff and leaves in the crank case.

There is no question about it. The engine needs to come completely apart. Dirt is your engines worst enemy. When you hole a piston, many of the vaporized pieces of aluminum go into the bottom end. This alone requires the engine be taken apart. Replace the rod and crankpin assy and the main bearings and seals.

Shadowpillar · Dec 10, 2006

Which clymer guide will I need, we're looking at a '74-'75 DT175 here. and I know it isnt piston port.I have the reed valve and all.
Yeah, I finally got the cylinder and head and all, the cylinder looks like it's fine, some build up near the spark plug hole and on the ports on the sides, other than that, it all looks good.

Also got the stock spark arrestor and exhaust decal :D

jason33 · Dec 13, 2006

the rod berring might be rusty as well- if not and it looks good i would use it -
pull up and down if its clean , there should be no up and down movement between the rod and the berring/crank pin
bike bandit has the parts finder that will show a microfiche pictures they will help even with a book

Shadowpillar · Dec 13, 2006

I think I might be safe with just a bearing replacement, the oil did protect the engine incredibly well, but I'll find out when I open it up, I also got the cylinder and head now, there are some slight wear marks on the side, and the more I look at this, it looks like the people before had a combination of a wrong spark plug with too much of an arc, and a lean mixture. the cylinder looks pretty well, shame I dont have a pic of it atm, I do have a blurry pic of the head, it seems fine sans some buildup.

Still, I might be able to just run oil through it or open it up and just clean it straight out so it doesnt have any debris left to destroy the engine later.

also, another interesting thing, there are two ports for the spark plug.. Well, one open, and one plugged up for an alternate diagonal entry for the spark plug.

What is the difference?

picture:
http://smg.photobucket.com/albums/v607/acidchat/100_0828.jpg

Ol'89r · Dec 13, 2006

Shadowpillar said:
I think I might be safe with just a bearing replacement, the oil did protect the engine incredibly well,
Still, I might be able to just run oil through it or open it up and just clean it straight out so it doesnt have any debris left to destroy the engine later.

also, another interesting thing, there are two ports for the spark plug.. Well, one open, and one plugged up for an alternate diagonal entry for the spark plug.

What is the difference?

QUOTE]

If you do not completely disassemble the engine, including the crankshaft, you WILL have future problems. Inside the big end of your rod is a needle bearing. All of the years of crap that got in the top of your engine went directly into the bottom end. Flushing out this bearing is very hard to do without leaving little bits of dirt and grit in there. If there is any dirt at all left in the bearing it will self destruct.

Why take your engine down to the last bearing and not replace the last bearing? :coocoo:

Sawblade nailed it. You can do it once the correct way or pay to do it twice. Your choice.

In regard to the two plug holes. Somebody most likely had a compression release installed in the head at one time. Just run an extra spark plug in there to plug the hole.

Shadowpillar · Dec 13, 2006

Ol'89r said:
Shadowpillar said:

I think I might be safe with just a bearing replacement, the oil did protect the engine incredibly well,
Still, I might be able to just run oil through it or open it up and just clean it straight out so it doesnt have any debris left to destroy the engine later.

also, another interesting thing, there are two ports for the spark plug.. Well, one open, and one plugged up for an alternate diagonal entry for the spark plug.

What is the difference?

Click to expand...

If you do not completely disassemble the engine, including the crankshaft, you WILL have future problems. Inside the big end of your rod is a needle bearing. All of the years of crap that got in the top of your engine went directly into the bottom end. Flushing out this bearing is very hard to do without leaving little bits of dirt and grit in there. If there is any dirt at all left in the bearing it will self destruct.

Why take your engine down to the last bearing and not replace the last bearing? :coocoo:

Sawblade nailed it. You can do it once the correct way or pay to do it twice. Your choice.

In regard to the two plug holes. Somebody most likely had a compression release installed in the head at one time. Just run an extra spark plug in there to plug the hole.

it's already plugged with a large bolt. I was thinking maybe yamaha had it set (this is a DT175A/B) so you could have an alternate placement of the spark plug. the top of the head is made so a spark plug can also stick out in that direction, it's interesting, and I'm wondering what's the point of it? other than mass produced parts for other bikes they had at the time..

also, would a '79's bearings work in a '74/'75 ?

another problem, I may or may not have a choice to do a somewhat half-assed job because of parts availability.

if anyone knows where I can get the parts for this bike, besides bikebandit, I'd be happy.

everything related to the piston, the connecting rod, and the bearings I can prolly find stock, but stock is pricey, a while back I could have gotten a compatible kit for $90, but that fell through.

dales298 · Dec 13, 2006

Most early Yamaha enduros had dual spark plug ports. You had the choice of running a compression release to help with braking or, you could run a protruding tip spark plug in case the standard plug fouled. You have to remember that these bikes were economical transportation and fouled plugs were a regular thing.

Dale

Shadowpillar · Dec 14, 2006

ah, that's a cool feature, I'll have to do that when I get it running :)

Shadowpillar · Dec 14, 2006

another question, anyone know if a 1975 DT175B could take a piston from a 1979 DT175F? and what the differences are between the two pistons?

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