Engine inspection

Engine inspection
Posted by AWedel on 26 Aug, 2013 10:22
I bought a '86 250 in a box. Top end in one box, bottom in another. Before deciding whether to part or rebuild, any suggestions on how/what to look for without tearing the bottom down completely. I'll have the top resleelved, but anything to look for there? Thx.

#1 Reply
Posted by Kyle T on 26 Aug, 2013 13:12
I'll get on this later tonight.

#2 Reply
Posted by PCS on 26 Aug, 2013 16:31
is it all there? that is what i would do, check to see if you have all the parts. post some pics so others can give you better inputs on the conditions of the parts you have.

#3 Reply
Posted by AWedel on 26 Aug, 2013 19:04
Here are some pics. It appears the case was split as there is evidence of white sealant at the seam. I can shift it 1-5. There is oil in the crank case, which I can see when I turn it over. The cylinder sleeve has an "ear" (skirt?) broken off (see pic), so I know it needs resleeving. The head has all kids of pitting. Any insights as to what to dig into deeper/inspect/measure are appreciated.

#4 Reply
Posted by Kyle T on 27 Aug, 2013 08:47
I was dead tired last night. I'll probably get it done tonight.
That bottom end looks dirty. You should probably split it. Especially with a broken sleeve.

#5 Reply
Posted by AWedel on 27 Aug, 2013 10:02
@Kyle T...that pic makes it look worse than it is (crappy BB camera). It appears the crank is pitted with rust, but it really isn't. The connecting rod is indeed rusty. How do I go about salvaging the head? How would it have gotted that pitted. Unfortunately, I know NOTHING as to the history of this machine. Anyway, any suggestions you might eventually have would be greatly appreciated.

#6 Reply
Posted by Kyle T on 27 Aug, 2013 10:13
You could get the squish re cut, but then you'd need the dome rechambered and cc'd.
Perhaps welding, remachining to stock specs, and decking the gasket surface would work?

#7 Reply
Posted by Kyle T on 27 Aug, 2013 19:11
OK. Here's the top end stuff.
You'll need a new:
Piston, rings, pin, clips, pin bearing, 09169-18006 washers, and sleeve.
You'll need to:
Measure the connecting rod little end bore. 23.04mm is your limit.
Measure the connecting rod little end lateral movement, while holding the big end of the connecting rod still. 3mm is your limit.
Rotate the crank and feel the crank pin bearing.
Rotate the crank and feel the main bearings.
Fix or replace the cylinder head.
Inspect the reed cage for cracks or other damage.
Inspect the reed pedal for cracks or other damage.
Inspect the intake pipe for cracks or other damage.
I'd still recommend splitting the cases to clean them out. Gonna suck big time if a piece of sleeve is hiding under the crank halves, and gets sucked up when you fire it up, and wedges itself between the new piston and new sleeve or somewhere else...

#8 Reply
Posted by AWedel on 29 Aug, 2013 04:02
So, I went through the boxes and didn't find the piston, wrist pin, or pin bearings. I'm wondering if something went really bad up top. So, yeah, I think I'll split it. Posts here suggest it's not too tough to do with the proper tools and being careful. Any tips? As for the head, how could the head have gotten so damaged? Looking on ebay, heads for auction there are dinged the same way. Does combustion over time just cause this to happen?

#9 Reply
Posted by MotorGeek - Jerry Hall on 29 Aug, 2013 05:13
The damage to the head is only caused by a mechanical failure.

#10 Reply
Posted by AWedel on 02 Sep, 2013 15:17
Thanks for the feedback. Another question, just curious, any ideas how the skirt/ear/tab/whatever on the bottom of the sleeve could have broken off (besides being dropped, perhaps)? Is it possible for something pretty violent to happen up top, beat-up the head, and also damage the sleeve like that. Otherwise, the sleeve ID looks normal (no gauges). By the way, it measured 2.794" (70.967 mm). How does resleeving work? Can this be resleeved back to the original 70 mm? Or must I go up to 71 mm?

Finally, I am going to split the case. I've never done this before, but want to try using the Clymer manual as a guide. Besides hunting down the broken piece from the cylinder, looking at the big picture, what else should I be careful to inspect while the whole thing is apart? Any other tips Alot of questions, but thanks...

#11 Reply
Posted by MotorGeek - Jerry Hall on 05 Sep, 2013 07:56
All of the Skirt/ears/tabs I have seen broken or **** happens during shipment, cylinder removal, or rough handling/dropping when the cylinders are in someones hands. The cylinder cannot be tilted very much when the cylinders are removed without the cases applying pressure on the tabs.

I have seen a few engines tabs "fall off" while the engine is running. I am confident that the engine was assembled with **** tabs at some prior time. When the piston clearance becomes excessive the piston exerts tremendous force on the **** tabs leading to eventual tab failure.

We find a lot of tabs that have cracks in them that have been running engines. We notice the cracks when we are cleaning the base gasket surface prior to boring. We bore cylinders using the cylinder base gasket surface as our reference not the head gasket surface like 80 % of the shops that bore cylinders. Using a clean burr-free base gasket surface guarantees the bore to be 90 degrees to the crankshaft.

The majority of the boring equipment that motorcycle shops have do not bore the cylinder square to the boring machines base. Be cautious if the boring machine the shop is using, looks like a drinking fountain with about a 1 1/2 inches shaft coming vertically out of the middle of the machine. The good boring bars are usually from the Automotive industry. Van Norman, Tobin Arp, Sunnen, Kwickway are some of the most popular companies that make high quality boring bars.

The majority of the Automotive boring bars require the cylinder head studs to be removed and mounted to the boring bar on the head gasket surface unless expensive custom spacer rings are used. The parallel spacer ring goes between the cylinder base gasket surface and the boring bar insuring "squareness" to the boring bar.

#12 Reply
Posted by AWedel on 05 Sep, 2013 16:22
@ Motorgeek--Keeping in mind I know nothing about this bottom end--that is, why it ended up in boxes--top end one box, bottom in another, I'm assuming you too would recommend tearing down the bottom end. (If you can't tell, this is something I'd prefer to avoid, but am willing to tackle it) Assuming that's the case, besides for looking for debris, are there any other things in general you'd inspect? Finally, as for the boring and resleeving. It seems you do that. If you'd like to shoot me a price via PM, I'd be glad to have a look. I prefer to use someone from the LT brotherhood rather than leave this to chance! Thanks.

#13 Reply
Posted by MotorGeek - Jerry Hall on 05 Sep, 2013 18:49
Quote from: AWedel on 05 Sep, 2013 16:22
@ Motorgeek--Keeping in mind I know nothing about this bottom end--that is, why it ended up in boxes--top end one box, bottom in another, I'm assuming you too would recommend tearing down the bottom end. (If you can't tell, this is something I'd prefer to avoid, but am willing to tackle it) Assuming that's the case, besides for looking for debris, are there any other things in general you'd inspect? Finally, as for the boring and resleeving. It seems you do that. If you'd like to shoot me a price via PM, I'd be glad to have a look. I prefer to use someone from the LT brotherhood rather than leave this to chance! Thanks.

I would recommend tearing it down. Inspect the cases carefully in the region next to the outside of the crank. There is not much clearance between the cases and crank and the cases are easily damaged when pieces of sleeve or piston skirts pass through this tight area. It is not uncommon for the cases to crack or distort enough to cause an air leak or suck oil from the transmission.

#14 Reply
Posted by AWedel on 08 Sep, 2013 16:49
Looking at the small end of the connecting rod on this machine, there is a worn radius at the, say, 12:00 and 6:00 positions on both the left and right sides. Is this acceptable? Notice in the pic the slight clearance between the little end and the straight edge. Is this the result of not running the RM bearing and billeted thrust washers? Anyway, please give me an idea of this is OK. The ID is within spec.

#15 Reply
Posted by Kyle T on 08 Sep, 2013 18:22
You mean 12 and 6 when viewed from the side? Yes. Those are supposed to be there.

#16 Reply
Posted by AWedel on 08 Sep, 2013 18:33
@Kyle--yes, 12 and 6, looking from the side. Thanks.

#17 Reply
Posted by AWedel on 28 Sep, 2013 19:59
Here is what I found when I split the case. There was indeed some shrapnel that bounced around. So much so, there is a hole in the case that opens into what seems to be an empty cavity in the casting. There are also gouges/scrapes around the case. Does anyone have an opinion as to whether or not this is fixable, and if so, worth fixing? Looking around ebay, there are a lot of cases out there, but most seem to have similar gouges (albeit, not holes). Thanks.