So, I know this isn’t car repair, but I thought there might be a bit of commonality–as well as the chance a fellow rider+wrencher could help me.
I’ve got a good “top end” and a (presumed) good “bottom end” for an old Honda parrallel-twin. I need advice on how to make one good engine out of both half-good ones.
My plan is to:
1. Remove engine from bike.
2. Move accessories over.
3. Take tops off both engines.
4. Put pistons from good top on rods of good bottom.
5. Slide on barrel and cyl. head; torque.
6. Turn engine by hand and check for obvoius issues.
7. Hot-wire to starter and check compression (that there is any).
8. Install engine on bike.
Just looking for advice! I’m particularly curious about how to install the timing chain and compress the rings (I have the tool). Never done either before!
If this doesn’t work, I’ll probably pay for a rebuilt, running engine and install–can’t keep driving the 17MPG truck!
Which engine (just curious). I guess as long as they’re the same, it should work. Course, you have the cam chain to deal with. This all assumes whatever messed up the bottom on one didn’t hurt the heads, and likewise whatever messed the head on the other didn’t hurt the bottom end.
They’re both CB350 engines.
The one picked up a BAD bottom-end oil leak that got worse, until it became unusable. Had shifting problems, too.
The other’s a $50 “salvage special” with top-end issues. If it works, great; if not, I’ll shell out the $$ for a rebuilt engine.
It’s been years since I’ve ridden or worked on motor, so take this with a grain of salt.
Why take the engine off the bike? Is one bike the “destination” bike?
Have you a Haynes or Clymer’s manual? You should.
For a 350 you might be better off buying a new bike rather than a rebuilt engine.
Get a manual, take top of motor off the one with the bad top end to see the best way to do the good one.
Put rings in cylinder and measure, maybe best to hone cyl and use new rings?
Plan on cleaning and rebuilding carbs.
Change oil after 50 mi or so and have fun and learn.
You need a shop manual…Honda’s are tricky engines to work on…You did not even mention the cam chain and it’s tensioning system…Good Luck…
Why rebuild/restore antique junk when for the same money you can buy a modern bike that are low maintenance and have decent suspension?
Hey caddyman, I douby the OP could get a new bike for the same money. have you seen the price of bikes lately? Even bicylces are running into the thousands. He already has the bike and the engines, he just needs to sit on the concrete and move his wrenches around in the just the right way, and you and I both know the feel of oil on our fingers hey my friend. And a Honda 350 is fast little bike too, and who makes anything like it anymore?
Uh, because he doesn’t want to ride a moped?
I have the Honda service manual in PDF form.
I’m fixing this bike because I like standards, and nobody makes standards anymore…it’s all either “fast plastic” or “rebel-mobiles.” I really like the mechanical simplicity of an air-cooled twin.
One thing I was wondering: the rings sit further up on the pistons than the point where the wrist pin goes to connect. Could I just leave the pistons inside the cylinder barrel, saving me from having to compress the rings?
Oh, and I’m aware of the cam chain…just referred to it as a “timing chain” in the OP.
It’s extremely easy to compress the rings on bikes like this, those pistons and rings are SMALL. I rebuilt my 250 Suzuki several times, but lucky for me (and it) it was a two stroke, 1/10th the parts of your CBs. I always liked the CB350:
I used to use metal bands that were used for strapping skids to commpress rings, cut a piece and make a u bend on each end,put over rings and grab both u shaped ends and squeeze rings and tap piston down.
I still would carefully take rings off and check to make sure they were not wore out before putting motor together,manual will have specs.
I say go for it.
In my day we compressed the rings with our fingers (you know, those wiggly things at the end of your arms).
What more could you ask for???
What more could you ask for?
Uh…$2800?
Sorry, but I couldn’t resist! Actually I love the KLR (love dual sports of 400-700cc generally), and I’ve already asked Santa for one.
He says he isn’t sure if I’ll make the “good” cut, though…I’m pleading extenuating circumstances.
Be advised that Honda has a penchant for obsoleteing motorcycle parts after 7 years. Your 8 step process sounds right to me. Hone cylinders, new rings and gaskets, and take time and care in timing the overhead cams.
It’s not just “a” 350, the CB350 was a cool model and is worth a little effort in fixing it up. Making one out of 2 is better on the environment than junking 2, also.