81 cb750k Trials and Tribulations

[sockmonkey20]

I started to take it apart i cant figure out how to get the timing chain that connects the crankshaft to the camshaft slackened. my dad doesn't work tomorrow so he is going to help me tomorrow so tomorrow i should know whats wrong with the engine i couldn't find a leak down tester nor  is my dad's air compressor working. so yeah im just slaving away at the engine.

[sockmonkey20]

with this bike when is the general rule of thumb for a top end rebuild. i really love this bike the kawa is so much faster but that only gets me so far, the honda in my opinion is so much better. the Honda has about if i remember correctly about 60k in miles, is that right around the time this bike needs a top end rebuild.

[motogrady]

Man, you have the engine out, why worry about when some other guy say's it needs a top end?

You're almost half way there, bop a set of rings in it, grind the valve seats, maybe replace the
timing chain while you're in there, and poof,
you have a strong running bike.

[sockmonkey20]

okay if im going to tear this engine apart instead of putting the OEM pistons do you guys think i should go with the aluminum piston and rods?(they dont build up as much heat therefore reducing the heat the engine puts out, any other suggestions on parts i could use or tools i will probably need, and the timing chains look and feel brand new they show almost no sign of wear

[motogrady]

when you get it apart you may find it only needs a set of rings.

i dunno, I like going OEM when messing with internals.

nothing against wisco or anybody, just seems they never hit the quality
one get's from the factory

[shinyribs]

motogrady wrote

... I like going OEM when messing with internals.

.... just seems they never hit the quality
one get's from the factory

Bingo!

[sockmonkey20]

I honestly think its only a burned exhaust valve in cylinder #4 and a blown head gasket, that wont cost much if thats the reason why this engine isn't running right, but first because i didnt think this entire project completely through i have to put it off until i can find a way to mount it without messing up the fins lol, im going to go to home depot and build something to hold it up so i can work on it lol.

[shinyribs]

sockmonkey20 wrote

.... but first because i didnt think this entire project completely through ....

You are not alone. We all feel your pain.

[seestheday]

I just built a wood box out of 2x4's and worked on it that way.  It fit nicely and was quite stable.

Oh, regarding the choke piece that broke - this happened on mine as well, and it might be the same piece.

The plastic is a part of the choke cable.  It connects to a metal piece on the bike.  The replacement choke cable I ordered came with a new piece and it worked great.

[sgtslag]

"Can SeaFoam destroy an engine if used in excess?"

No, you can actually run an engine on pure SeaFoam -- it is 100% petroleum products.  An engine will run a bit rough on pure SeaFoam, but it will run.

SeaFoam has a lot of uses, listed on the can, and their web site.  Basically, it will absorb water (both in oil, and the fuel system); it will stabilize gasoline for up to 12 months (their claim, not mine); it will dissolve varnish, and carbon deposits, within an engine (when added to the crankcase); it will do other things as well, but those are the high points.

I added it to the engine oil, on my '79 K model, at 9,600 miles, ran it five minutes on the center stand, idling, shifting through all gears, to circulate it though the transmission, as well as the engine -- turned my caramel-colored oil to coal black.  I changed the oil, and the filter.  At 15,000 miles, I repeated the SeaFoam treatment:  after 300 miles, the oil never changed color, no sludge was dissolved.  Never did it again.

Back in the 80's, oils were SF standard, today they are SN rated.  World of difference in modern oils, compared to the old SF standard!  Newer oils last longer, work better, and produce far less sludge.  Treat an engine crankcase once every 50,000 miles, with SeaFoam, with regular oil/filter changes every 3,000-5,000 miles, and you are golden.  Cheers!