PDA

View Full Version : How to prep new short block when installing


Roger
08-15-2007, 10:58 PM
In a recent thread, I provided a narrative of troubles I had with my LawnBoy DuraForce engine. The result was engine failure, requiring a new short block.

The block arrived today by UPS. We finished our mowing route early today, and were home by 5:00. So, I started the install of the new short block and hour later.

I work outside and a platform. By 8:15 a shower arrived and I had to pack up before I was completely done. I hope to finish the project tomorrow evening.

I was surprised at the lack of lubrication in the cylinder of the new block. The walls are dry. Since I have a day before completing the install, and still have not put the head back on, I thought I would ask about preping the walls before attempting to start the engine.

Since the walls appear to be without any lubrication, the first few strokes after starting could be brutal. Can anybody suggest a procedure to lube the walls before starting? Or, is my concern ill-founded?

My thought was merely to rub the walls down with engine oil before installing the head. Yes, it would probably smoke after starting to burn off the oil, but at least the walls would have some lube on the first few strokes.

Ideas or comments? Thanks.

P.S. I have taken some pics of the procedure to tear down and do the install. When I have a bit more time, I will post some of them, with narration, so that it may help somebody else who is considering such a project.

SLR
08-16-2007, 12:23 AM
I do reckon you have answered you request,with pre-oiling before assembly.

khouse
08-16-2007, 12:31 AM
The first few tanks of fuel should be ran in the 32 to 1 ratio. Then you can run your normal mix ratio. That's just what I do.

SLR
08-16-2007, 12:46 AM
Oops,forgot these were 2strokers!..eliminate my previous "pre-oil'n" cyl.

Restrorob
08-16-2007, 07:51 AM
My thought was merely to rub the walls down with engine oil before installing the head.

That's exactly what you want to do using just a rub of 2 cycle oil, You never want to start a new/rebuilt engine dry.

Roger
08-16-2007, 10:20 PM
Update:

I finished the install this morning. The machine is back up and running. We had some heavy rain overnight, making mowing conditions difficult to start the day. So, I decided to take enough time while turf was drying out to finish.

Thanks for the comments (restrorob, khouse) regarding preping and break-in period. I did bathe all surfaces with 2 cycle oil, and am running 32:1 fuel mix to get it started.

All total, it took me about four hours of time. I just don't know where the time went, but I took my time, being methodical about my work. I don't do these projects every day, so had some learning to do along the way.

Thanks for the help. Here's hoping that I'm finished with repair work on this machine for the rest of the season!! I'm not sure I have any more emotional energy to put into this simple machine.

A few pics for now, more later when I have time to prepare.

Roger
08-16-2007, 10:23 PM
A few more:

Restrorob
08-16-2007, 10:41 PM
Rodger,

I'm not up on 2 cycles as I am on the 4 cycles but unless that engine has been sitting a while I'd say it was run lean. That cylinder looks awfully dry, Possibly oil mix too lean or carb leaning out a little ?

Did you happen to check/clean the carb while it was off ?

Roger
08-17-2007, 07:18 AM
Restrorob, your observations are keen. Yes, I felt the same way when I opened up the cylinder cavity.

When the problem happened, the engine was running well. Only in the last few minutes of operation was the operation degrading.

This machine has been a major headache all season. Here are a couple of other threads that detail the problems:

http://www.lawnsite.com/showthread.php?t=177356

http://www.lawnsite.com/showthread.php?t=195565

The carb was a major problem, but I felt it was finally resolved. During those carb problems, the plug color was very light, nearly white. That indicates a lean operation to me. However, when the seizure finally happened, the plug color was good, a brown-grey, perhaps a bit of red included. The color on the inside dome of the head is probably the best description.

It is certainly possible the cylinder wall problem all started during the time of the carb problems. The damage was begun, and finally expressed itself fully at the point of seizure.

I am sure that you, and other mechanics, chuckle (cringe ?) at my amateur style of engine repair. I'm sorry, but that is about the best I can do for my skill and training (none) level.

Clearly, this machine would have headed to the bone yard if I had to take it to a repair shop for this work -- simply too much labor cost. Now, I am counting on another 300-400 service hours to get me through the rest of this season. This machine will not start another season as my primary hand mower.

Breezmister
08-17-2007, 11:28 AM
I am sure that you, and other mechanics, chuckle (cringe ?) at my amateur style of engine repair. I'm sorry, but that is about the best I can do for my skill and training (none) level.

On the contrary Roger, you did a great job ! I have read with great interest
all of your threads. In this little hole in the wall shop I now work in, I might see one or two LBs a year, always minor stuff. You have taken more time with your repair then I have ever done with LBs in the last thirty years:cry:
Keep up the good work

Restrorob
08-17-2007, 01:28 PM
I am sure that you, and other mechanics, chuckle (cringe ?) at my amateur style of engine repair.

Not at all Roger, We all must do the best we can.....Hats off for a job well done !!!

Now, I do cringe when a customer tears into a unit then decides they can't handle the job then brings it up to me in a box.

Eric D
08-17-2007, 02:27 PM
Now, I do cringe when a customer tears into a unit then decides they can't handle the job then brings it up to me in a box.
Rob,

Don't forget they expect a discount because they already have it apart for you! Don't laugh, I have had this happen.:dizzy:

Roger,

Nice job. It is always nice to see someone save a unit that would normally be in the junk heep if taken to a shop.

Regards to all,

Eric D

khouse
08-17-2007, 06:56 PM
Hats off to you! Natural light is the best for working on equipment. Most guys are stuck in a hot building. Great job!

dutch1
08-17-2007, 09:21 PM
It's good to get resolution to your problem. Job well done. I worked in a LB shop and did numerous LB's over the last 10 years and that is the first commercial LB with a Duraforce that I have seen. We saw numerous commercials with the Suzuki 2 stroke however.

In response to a previous reply regarding mix ratios, unless I'm terribly mistaken, LB has always been 32:1. We had customers use Optimol at a higher gas to fuel ratio with no problems but we always recommended sticking with LB oil at recommended rates. I'd say that 90% of LB engine failures were straight gas failures. I caught 3-4 of those failures, even though there was a mix in the tank. Those customer insisted that the engines were not straight gassed since there was a mix in the tank. I'd pinch off the fuel line, remove the carb and pour the gas from the carb into a clear gas jar. Bingo--straight gas.

I agree with others, from looking at your pictures, that you had a lean mix problem or a lean gas/air problem. I would be interested in seeing what what the case halve surfaces look like when/if you separate the block. Unless you you had a problem carb causing the lean condition, I would suspect a case half leak or a top/lower seal leak.

Again, congratulations on a job well done!

Dutch