Cylinder Block Swap Questions

Hi There.

I'm very depressed today. I just found out that my cylinder block is in a bad way and needs to be re-bored to one-over. I just don't have the money to pay for the rings, new pistons, and boring fee. I was thinking about trying to find a new cylinder block (see my post in the Parts Wanted Forum) but I don't have much experience with this end of the bike and have a couple of questions:

1) Am I even right in thinking that if can find a block in decent condition and within tolerances that I can just use my pistons (with new rings) and cylinder head?

2) If I end up having to scour wreckers how can I check if a block is okay? Do I have to bring my pistons along and feeler gauge to check the gap? What should it be?

Any advice would be greatly appreciated. Whatever happens it looks like the bike is off the road (again!) for a while - just when I had it running the best it ever had! I am extra depressed because I was supposed to be leaving for week-long trip down to Deals Gap in Tennessee next week, which is now canceled. Sorry about the sob-story. Just venting.

Jimmytime

 

how much is the machining and parts?. Might be cheaper to just find another engine complete. Or have the bad cyilnder sleeved.

MN

 

1: Yes but next to impossible.

2: Yes and it's probably an exercise in frustration; not to say you might get lucky.

For that money, I'd just look for another motor. If you find a decent cylinder block see if you can get the pistons WITH it and use those.

Finding a block that will fit your pistons without a bunch of machine work is not altogether that likely. Finding new oversize pistons (or new pistons period) could also prove to be a challenge.

 

Hmmm... I appreciate your help, but you guys are making me even more depressed!

The pistons are just over $300.00, the rings pushing $200.00 and the re-bore I got quoted at $80.00 a hole! (Cdn)

A couple more questions - I've heard of "sleeving" and can imagine what it means, but am unclear on the specifics. Does that allow you to use your pistons? Do they bore it out and then sleeve it back to spec?

Replacing the motor - you mean the block, head, cams, valves everything right? I've never shopped for a motor by itself before - is there any way that you can "test" it if it's not in a bike? Compression etc.? What could I expect to pay for something in decent shape?

 

My point; you're looking at dropping almost $1K if not more. "Sleeving" gets even more expensive.

I (we) mean the whole bloody lump, to quote David Hobbs.

You can do a compression test on a motor out of the bike; I've done it more than once. You usually need to bring your own battery/cables; on one occasion I had to bring a starter (he sold it already.)

You can usually find decent motors for anywhere from $150-$500. The best thing after the compression test is to try to determine why the bike was parted out to begin with. You don't want to but a unit with a crumbling primary chain tensioner or a blown 2nd gear. The again, a motor with good compression could prove to be a valuable donor too.

 

The machine shop I have used for sleeving usally can do it for the same or less than the price of boring and pistons. Granted your not saving much but if your pistons are good and useable so you are looking at rings and gaskets. Thats about the best you can get out of that situation. I would price shop , the internet is a big place you never know what you'll find.

As far as a different engine is concerned. That would be your cheapest option if you can find a good one. You might be able to find a non runner and part it out to re-coupe your costs. I think thats what i would do.

MN

 

Thanks guys!

I'm feeling optimistic! I think I inquire about sleeving while actively looking for a "new" motor.

 

Good Luck,

Let us know how it all works out. You know once you start checking prices that always leads to finding the same thing even cheaper.

MN

 

Drum Hill Cycle
Nashua
New Hampshire
(603) 577-5532


http://www.drumhillcycle.com/index.cfm/ ... /3,3848883

 

Thanks for that Rick! It brings up another question I had: my current bike is non-YICS - can I drop in a YICS motor? Will my pristine, vacuum synced carbs that I've spent so much time and money rebuilding and cleaning work? Please say yes.

 

Yes, you can! You will need to retune the carbs to match the new engines needs but it is completely doable.

 

It sounds like you've already checked this but are you sure your pistons and cylinder aren't already oversized? (If they are things could get a little simpler)

 

Thanks for all the info - that fact that I can use a 750 engine makes me feel even more optimistic! So many more options! If I could ask a couple more questions about going from a 650 to 750:

From this forum I gather that I may need to re-jet my carbs - does anyone have a staring off point? Currently I am 2 over in both my idle and main because I have a K&N filter and a 4 into 1 exhaust. Does anyone have a starting point for going up from a 650 to 750?

Also, because my bike is not YICS, is it true that I will have to change 2 of my rubber intake manifolds?

Finally, what about my starter and alternator? Most of the engines I've seen have those removed - will the ones from my 650 work on a 750?

Thanks again! I love this forum!

ps fore4runner - yeah, they are stock unfortunately! I wonder if they are worth anything...

 

Rick. Thanks for sharing the web site. It was definitely worth the click to see all those great engines!

 

Man Drum Hill has some neat stuff but his prices are way high.

 

Starter and alternator are compatible. Intake manifolds are not.