646-75lbh restore

Troubleshooting, rebuilding, repairing Onan engines.
User avatar
Spike188 Canada
Posts: 1058
Joined: Sat Mar 06, 2021 12:58 pm
Location: Ayr Ontario
Has thanked: 5602 times
Been thanked: 4041 times

646-75lbh restore

Post by Spike188 »

This summer a 646bh with a ccka engine was purchased. The engine was missing a lot of components but thanks to Boomer, that problem was taken care of.
20200718_155024rs.jpg
20200718_155024rs.jpg (419.84 KiB) Viewed 10518 times
The biggest surprise was pulling the flywheel and not seeing an armature.
20210306_202133rs.jpg
20210306_202133rs.jpg (493.3 KiB) Viewed 10518 times
Plans were to have the engine back on the tractor by last fall, well here it still sits on the back bench.
20210306_202158rs.jpg
20210306_202158rs.jpg (485.8 KiB) Viewed 10518 times
I love it when a good plan comes together. It just doesn't happen often enough.

Eugene
Spike Colt - 9 & 10, Case - 108, 118, 444, 446, 448, 646, 646bh, Ingersoll 4016, 4118AH
User avatar
Eugen Canada
Posts: 5141
Joined: Wed Mar 03, 2021 2:52 pm
Location: Port Mcnicoll, Ontario
Has thanked: 11934 times
Been thanked: 16195 times
Contact:

Re: 646-75lbh restore

Post by Eugen »

Hi Eugene! I for one am looking forward to your restoration through which I will live vicariously. What do you think, should we perhaps create a Restorations forum subject?

I do want to expand on the subjects, as the current ones I created in hurry to have a starting point.
Last edited by Eugen on Sun Mar 07, 2021 10:22 pm, edited 1 time in total.
Case 224, 444, 644, 680E
Kubota B26 :blush:
User avatar
Harry United States of America
Posts: 1483
Joined: Sun Mar 07, 2021 8:33 am
Location: Lockport,NY
Has thanked: 9159 times
Been thanked: 6197 times

Re: 646-75lbh restore

Post by Harry »

I'm looking forward to seeing your restore Spike. I have a 1977 646 with loader and rototiller.
Keep the Peace
Harry
1973 444, 1974 644, 1976 446, 1977 646, 1986 226
User avatar
Spike188 Canada
Posts: 1058
Joined: Sat Mar 06, 2021 12:58 pm
Location: Ayr Ontario
Has thanked: 5602 times
Been thanked: 4041 times

Re: 646-75lbh restore

Post by Spike188 »

Harry, You know me from the other site,

Eugene (not to be confused with Eugen even though he is the best)
Spike Colt - 9 & 10, Case - 108, 118, 444, 446, 448, 646, 646bh, Ingersoll 4016, 4118AH
User avatar
Spike188 Canada
Posts: 1058
Joined: Sat Mar 06, 2021 12:58 pm
Location: Ayr Ontario
Has thanked: 5602 times
Been thanked: 4041 times

Re: 646-75lbh restore

Post by Spike188 »

Eugen wrote: Sun Mar 07, 2021 1:30 pm Hi Eugene! I for one am looking forward to your restoration through which I will live vicariously. What do you think, should we perhaps create a Restorations forum subject?

I do want to expand on the subjects, as the current ones I created in hurry to have a starting point.
Restoration as a forum subject makes sense.

I will put the Backhoe restoration under it when created.

Eugene
Spike Colt - 9 & 10, Case - 108, 118, 444, 446, 448, 646, 646bh, Ingersoll 4016, 4118AH
User avatar
Spike188 Canada
Posts: 1058
Joined: Sat Mar 06, 2021 12:58 pm
Location: Ayr Ontario
Has thanked: 5602 times
Been thanked: 4041 times

Re: 646-75lbh restore

Post by Spike188 »

Following the Onan service manual steps for engine assembly, the main and cam bearings were the first to be installed in the block. The bearings were placed in the freezer next to the ice cream during an off site service call. You know a person is stoked when the engine rebuild took precedence over ice cream. Not only were the bearings installed but the pistons also.

With the main bearings in place the crankshaft and thrust bearings were installed.
CCKA Thrust bearing backlash.jpg
The first crankshaft backlash check with the gage came out at around 0.027". The range was to be 0.006" to 0.012". After a moment of panic and a bit of thought, it became obvious why Boomer had sent 2 rear bearing plate gaskets. One measured 0.018" and the other was 0.009" thick. Switching to the thinner gasket brought the backlash down to 0.012 which was ok but not acceptable. Having a roll of 0.005" steel shim stock, there was a "why not try it" moment, the manual does recommend shimming.
CCKA thrust bearing shim.jpg
A 2" id shim was quickly cut with a new box knife blade
CCKA Thrust bearing backlash.jpg
and the final measurement was just over 0.006". That backlash will be good for the life of the engine.

Now the trusty feeler gage moves on to the next step. Fitting the rings.
ring showing on piston.jpg
The original pistons were worn to the point that the rings could be seen between the piston and cylinder wall. Once again Boomer Influence came into play. When ordering pistons he recommended 0.020" oversize. It turned out to be a good call because there is a very small rust pit in one of the cylinders, likely caused be water sitting in it at some time.
CCKA ring gap.jpg
A piston was used to punch the new rings perpendicular to the bore.
CCKA ring gap measure.jpg
The spec's for ring gap is 0.010" and the rings were a perfect fit with no modification needed.
CCKA Pistons in.jpg
With the 0.020 oversized pistons installed in the fresh bore, things are looking good.




It feel good to have this project moving forward again.
Spike Colt - 9 & 10, Case - 108, 118, 444, 446, 448, 646, 646bh, Ingersoll 4016, 4118AH
User avatar
Eugen Canada
Posts: 5141
Joined: Wed Mar 03, 2021 2:52 pm
Location: Port Mcnicoll, Ontario
Has thanked: 11934 times
Been thanked: 16195 times
Contact:

Re: 646-75lbh restore

Post by Eugen »

Niiice! :thumbsup:

Questions:

Did you have the valve seats done too?

Was the crankshaft ground to the next smaller size?

How did you orient the ring gaps, in any particular way or random?

:geek:
Case 224, 444, 644, 680E
Kubota B26 :blush:
User avatar
Spike188 Canada
Posts: 1058
Joined: Sat Mar 06, 2021 12:58 pm
Location: Ayr Ontario
Has thanked: 5602 times
Been thanked: 4041 times

Re: 646-75lbh restore

Post by Spike188 »

Eugen

The crank was good so it went back with STD bearings. Top 2 rings are gapped 180 degrees and parallel to the crank shaft. Oil rings are at 90 degrees to the crank. I will be doing new guides and valves and lapping the seats.

Spike
Spike Colt - 9 & 10, Case - 108, 118, 444, 446, 448, 646, 646bh, Ingersoll 4016, 4118AH
User avatar
Eugen Canada
Posts: 5141
Joined: Wed Mar 03, 2021 2:52 pm
Location: Port Mcnicoll, Ontario
Has thanked: 11934 times
Been thanked: 16195 times
Contact:

Re: 646-75lbh restore

Post by Eugen »

Spike188 wrote: Thu Apr 29, 2021 10:38 am Eugen

The crank was good so it went back with STD bearings. Top 2 rings are gapped 180 degrees and parallel to the crank shaft. Oil rings are at 90 degrees to the crank. I will be doing new guides and valves and lapping the seats.

Spike
Oh, new guides! The old guides were out of spec I guess. I'm a little intimidated by the guides replacement procedure, worry that I mess everything up real good if I try to take the old ones out on my k321. I'm not sure either if they're ok, don't have the right gauges to measure them :(

Regarding the oil rings, do you take the thrust side of the piston into consideration at all? I don't have experience with this, so I go by what I read on the world wide webs
Case 224, 444, 644, 680E
Kubota B26 :blush:
User avatar
Spike188 Canada
Posts: 1058
Joined: Sat Mar 06, 2021 12:58 pm
Location: Ayr Ontario
Has thanked: 5602 times
Been thanked: 4041 times

Re: 646-75lbh restore

Post by Spike188 »

I did take the Onan wear patterns into consideration for all of the rings. Others may have input on the best layout of the rings.

Spike
Spike Colt - 9 & 10, Case - 108, 118, 444, 446, 448, 646, 646bh, Ingersoll 4016, 4118AH
Post Reply