Author Topic: Engine Unstuck Finally! - What next? (Read 3666 times)

Blasbo · « **on:** January 21, 2012, 04:22:18 PM »

My 750 K7 is finally unstuck

I never really thought about what I need to do next. I had to take the head and cylinders off. It's nasty and rusty but in my very inexperienced eye it doesn't look too bad. What do I need to look for? What do I need to measure to make sure it will function? I've downloaded the service manuals. Do I need to get a micrometer and measure everything?

cmonSTART · « **Reply #1 on:** January 21, 2012, 04:52:07 PM »

What are you looking to do with the bike?

The first thing I would be concerned with is just how badly rusted or pitted the cylinders are. Then you'll want to start measuring the cylinder bore to see how good it is, whether it's egged or OK. Check your valve seats and guides. See just how worn the engine is.

Fun stuff!

Stev-o · « **Reply #2 on:** January 21, 2012, 06:05:10 PM »

Can you post some pics? What's your plan with the bike, how 'bout a big bore kit?!
[$110 for the parts on eBay]

Blasbo · « **Reply #3 on:** January 21, 2012, 08:25:27 PM »

cmonSTART
My goal is to make it a reliable runner, nothing elaborate at this point. What do I need to measure the cylinders with? Can you give a specific recommendation? I've seen calipers range from $25 to $500. I don't mind spending the money if I need to, but no sense in doing so if I don't.

Stev-o
I read not long ago that rings are scarce and expensive for K7/K8. If I need rings I probably will get an 836 kit. If I don't need to spend the money right now I probably won't.
Here's some pics, I haven't done much except spray some PB Blaster and wipe down with a cloth. Let me know what in particular I need to look at.

Thanks to both of y'all.

ekpent · « **Reply #4 on:** January 21, 2012, 09:16:51 PM »

Your cam chain guide and your piston rods are covered really bad with rust,not a good sign at all, I am sorry to point that out. Looks like a lot of water or moisture has gotten into the bottom end,Gears and crank and other goodies down there may be polluted also. Think you better split the case and take a little better look in there or at least remove the oil pan for a peek for starters to see if its worth saving.

VTCBike750 · « **Reply #5 on:** January 22, 2012, 06:01:55 AM »

From the looks of it, your cylinders have a good amount of rust on them too. You could considering honing them and seeing what they look like afterwards, but it may be an over bore in the end. Would plan to replace the rings regardless.

To measure the cylinders you can get a set of used Telescoping gauges on Ebay.

I found this post helpful: http://forums.sohc4.net/index.php?topic=77422.0.
This is a good intro video on how to use them: http://youtu.be/qDNP25PtBqM

I just picked up a set as I am nearing what you are doing. I ended up getting a random set of Starrett, Lufkin, and General gauges for around 15 bucks on ebay.

+1 on what Ekpent said.

chewbacca5000 · « **Reply #6 on:** January 22, 2012, 01:34:50 PM »

+1 on what Ekpent. I'd get a flashlight and get a better look in there. If there is that much rust in the bottom end it might make more sense to just start off with a different engine. I've seen post on this site where guys take sandcast out of swaps and bring them back to life. The thing is your bike is a K7 and will never be able to pay you back the effort. Unless you have extensive experience doing engine rebuilding it might be best to get another K7 in better condition as a starting point. Just my 2 cents.

Blasbo · « **Reply #7 on:** January 22, 2012, 06:56:30 PM »

So here's a picture with the oil pan taken off. I didn't see much rust up in there, but I guess I should split the cases and see what it looks like. Not sure if I should do that next, or try to hone the cylinders, or try to clean them up and see if they're pitted from rust or measure to see if they are out of round.
Suggestions?

Tews19 · « **Reply #8 on:** January 22, 2012, 07:21:23 PM »

I have no engine tear down experience, but god that is odd. The top end is nasty as hell, bottom end looks really clean ....... If i was you I would be saying WTF!!!!!!!!!!!!!!!!!!!!

faux fiddy · « **Reply #9 on:** January 22, 2012, 07:37:43 PM »

I would find a pan big enough for the head and soak it in solvent. Spray and wipe isn't going to get it clean. I would also get a spring compressor or arbor press and take the valves out. A wood block with holes driled in it makes a nice place holder for keeping the valves in order. Clean up all the ports, use a file to get rid of carbon and casting marks and smooth things out where air comes in and out. Plan on at least lapping the valves with valve grind paste, since you're in there anyway.

Do as I say and not as I do on this: Be careful not to break any fins off at the corners ( or anywhere else for that matter.)

scunny · « **Reply #10 on:** January 23, 2012, 04:43:24 AM »

I wouldn't bother buying measuring tools for the bore etc. take your cylinder block to a decent motor recon outfit and they will measure it up for you.

Stev-o · « **Reply #11 on:** January 23, 2012, 06:03:20 AM »

Is the trans shifting normally? May not need to split 'em?

cmonSTART · « **Reply #12 on:** January 23, 2012, 09:34:52 AM »

Quote from: scunny on January 23, 2012, 04:43:24 AM

I wouldn't bother buying measuring tools for the bore etc. take your cylinder block to a decent motor recon outfit and they will measure it up for you.

Just looking at the pitting I wouldn't bother. You're probably looking at oversize pistons if everything looks OK in the bottom end.

Blasbo · « **Reply #13 on:** January 23, 2012, 09:36:19 AM »

After sleeping on it I'm thinking my first step should be to try and clean up the cylinders and see what I've got as far as pits and grooves. What can I use to do that? Would green scotch brite be too abrasive?

Stev-o, it shifts through the gears with no problems.

scunny, that's a good idea. I will ask around but I don't know anyone locally. I am pretty much dependent on the forum for advice.

fiddy, I was already planning on lapping the valves. Thanks for the tips.

Tews, I figure it was left out with the no plugs in the holes. Top end rusted up but the bottom end was sealed by the pistons...

cmonSTART · « **Reply #14 on:** January 23, 2012, 10:50:41 AM »

A hone on a cordless drill will work well for that. Just do a little at a time and check your progress.

grasscutter · « **Reply #15 on:** January 23, 2012, 11:52:16 AM »

I'd go about it differently, if it were mine. Spend virtually no $$.. put it back together and ride it. Listen to it, see what else needs done. Compression test is real indicator of head, valve work.

I hate seeing people step into their first tear-down and end up with a 'basket case' project listed on craigslist.

If you get some riding in, it might give you motivation to start purchasing all the parts for a rebuild. Then when you have time.. tackle it in a prompt fashion.
1st timers tearing into something, then having to order parts, then doing the next step, then waiting on more parts.... you get the idea. Some times those projects end up collecting dust.

Us older guys have been there, and usually have more than 1 bike, so we can wrench, and not have to stop riding!

Anyway.. just another idea.

Blasbo · « **Reply #16 on:** January 23, 2012, 12:01:06 PM »

Grasscutter, I like the way you think! That is my original intention with the bike, to learn how to work on bikes and have a relatively inexpensive ride.
If it was your bike, what would you do next?
I really appreciate everyone's advice and will take it all in consideration.

grasscutter · « **Reply #17 on:** January 23, 2012, 12:57:28 PM »

Others have covered this.. clean, clean, clean. Elbow grease is CHEAP! A few gaskets. A good repair manual. If it doesn't run and there's major issues, you may not end up rebuilding it anyway. Sometimes you can find a good donor engine for way less than the parts, machine work, etc.

(Although if you end up loving cycling.. you'll get a rebuild in eventually!)

There's plenty of guys on here (myself included) that have put many miles on engines they 'unstuck'. Don't count your chickens.. right?... it doesn't always work out like that.

Blasbo · « **Reply #18 on:** January 23, 2012, 01:03:15 PM »

OK, this is a really noob question, but what do I clean the insides with? I was thinking PB Blaster and green scotch brite but I didn't know if that was too abrasive. Or soak it in kerosene?

grasscutter · « **Reply #19 on:** January 23, 2012, 01:31:21 PM »

Sadly it does look like quite a bit of rust on the cylinders. But can't verify that just in pics.

Super cheap option: buy a hone (that attaches to your drill). Do it yourself. (and you learn how to run a hone).
(and if you find serious deep pits.. then you know you've got a rebuild on your hands.)

Not sure scotch brite pads are going to tackle that. Steel wool maybe? I'd stick with a hone.

Any machinists please jump in.. if honing is not correct 1st step here.

cmonSTART · « **Reply #20 on:** January 23, 2012, 01:43:04 PM »

Great info on honing a cylinder here:

http://www.dansmc.com/hone_cyl.htm

It really isn't difficult at all and doesn't take too long.

VTCBike750 · « **Reply #21 on:** January 23, 2012, 07:01:33 PM »

Nice link!

ekpent · « **Reply #22 on:** January 24, 2012, 07:08:46 AM »

Quote from: Stev-o on January 23, 2012, 06:03:20 AM

Is the trans shifting normally? May not need to split 'em?

You answered that it is shifting normally with no problems but that would be kind of hard to determine on a seized engine.Have you carefully looked down into the cases to see if the piston rods are completely covered with rust down to and around the crank area. What did the oil look like that you drained out,was there any visible water in there and what type of sediment did the oil pan contain. I would be afraid that if the bottom end was not cleaned out thoroughly,there was major sediment,rust, etc in there,that if put back together and started, it would possibly clog the tiny oil jets to the head and cam area turning them into burnt toast very quickly. On a side note have you cracked the carbs open yet to see if they got filled with water. There is another post now showing some filled with a white powdery corrosion that is caused by that.

News:

Author Topic: Engine Unstuck Finally! - What next? (Read 3666 times)