[dhosler]

Hi Friends,

I have recently acquired a Case 446 - 1976 vintage. Previous owner had it stashed in his barn for the last 8 to 10 years. When he parked it, he said it could hardly stay running.

This unit has the Onan BF engine in it. I am wondering what sort of things I should do prior to attempting to start it up. Here is a list of things I have done so far:

1. Compression test yielded good results. 115psi for each cylinder.
2. Replaced both spark plugs with new, and gapped appropriately.
3. Replaced both spark plug wires with new. (old ones were melted through on the exhaust all the way to the center core.)
4. Checked and adjusted point gap from 0.015 to 0.020.
5. Replaced both wires from the coil due to large bare spots in the insulation.

I plan to change oil, but wondered if I should try to start as is, and change oil when it has been warmed up (if it starts, that is). Also, curious as to what else to check and/or replace.

Thanks all,
-Dan

 

[gator_rider2]

Pull heads de carbon adjust valves clean out carburetor while off take apart intake halfs reseal clean engine cooling fins. Replace fuel line and filter clean out fuel tank.

Engine oil Drain now and again at half interval oil been in engine 9 years 9 months to long.

 

[Hydriv]

I hate to start off this reply in this manner but it is very dangerous to just spin over an engine that has sat around for ten years. Onan's are boxer engines -- horizontally opposed cylinders. Carbon deposits can flake off, fall to the bottom of the cylinder and create a lump of material that can break that side of the piston when it comes to top dead center.

No matter which engine you have, it is smart to remove the spark plug/s and then rotate the engine by hand for two full revolutions. If you hit a hard spot....STOP. Remove the head/s. Clean out the crap and save yourself the cost and agony of broken piston/s.

So.... lecture over.... let's move on.


Older Onan's often came with a composite material as the floatation material in the carb. The so-called modern fuels with alcohol cause the composite to expand, rub the sides of the float chamber and cause flooding and other issues. Brass floats are available if you find that you have a composite float. You might want to investigate this right now and clean out the float chamber with your shop vac. LOOK for congealed fuel and signs of varnish that may be plugging up the jets. A can of Seafoam is a good thing to have on hand. Fill up the float bowl with the Seafoam and let it sit for a couple of days to soften the varnish and other junk left behind when the old fuel evaporated. Seafoam in the fuel tank is another good move.

I know that you are anxious to see if this runs but patience is needed. Check the inside of the fuel tank for residue. Suck out any old fuel if it is still around. If the tank is dry, then vacuum out any debris. Check the fuel lines to see if they are rock hard or not. If so, pull the fuel tank out, install new lines all the way to the fuel pump on the carb. Install an in-line fuel filter in the correct direction between the tank and the carb. Check the outlet of the tank for a fuel screen. If it has one, destroy it and just rely on the in-line filter. STAY with the spring clamps on the fuel lines. Resist using gear/worm clamps.

Fill the tank with fresh, regular gas and add some Seafoam in accordance with the instructions on the can. Make sure that the float level is set properly and that the needle and seat are not stuck together. Shove a rag in the throat of the carb so that you don't drop screws down it.

Once all of that is done, put the carb back together. Drizzle an ounce of fresh gas down the carb throat and spin the engine over with no choke. See if it lights up a few times. If so, then close the choke and try it again. You should be outside and away from buildings while doing this and you should have a fire extinguisher nearby just in case.

How well the engine idles and performs throughout the throttle range will dictate whether the carb needs to be soaked for 48 hours in a true carb cleaning solution or not.

Once the engine is up to temp, you can shut it down and drain the oil. Refill with straight 30W and change the oil filter if you have one.

 

[dhosler]

Hi Gents,

All excellent ideas. I would be foolish to ignore such good advice. Here's what I did after I read your replies...

I have taken the gas tank out, and given it a thorough cleaning. I also have taken out all the old fuel line and will replace with new - it was rock hard and gave no flex whatsoever. I bought a new fuel filter, too, with the pinch-style clamps.

I also chilled out for awhile, and re-read the "Onan Technical Manual" from this fine form, and came across many good morsels of information. While on this subject, I would like to thank the moderators and all parties responsible for providing such good manuals for us to download and peruse.

In the evening hours, I couldn't sleep so I went back out to the barn for more tear-down. I pulled off the intake manifold, valve covers, and cylinder heads. Cylinder walls appear to be in good shape, but valves are very carbonized as y'all suspected. I'll yank the valves once I visit my neighbor for his spring compressor.

All the while, I'm making a shopping list of gaskets, seals, and odds n ends I'll need to be buying to build this motor back up. Again, I refer to your "Where to Buy Stuff" thread, and find it very useful.

I agree with Hydrive's advice to remain patient and not get into a rush during this time. I know the decisions I make now will have long term ramifications in the life of this engine. While I would like to see this engine running, It is a hobby and not a race. Thank you for keeping things in perspective for me.

Today, I hope to clean up the carbon deposits on the cylinder heads, and tear into the carburetor to see what type of float I have.

One questions I have, though. Gator_Rider2 mentions I should "reseal the intake halves". Can you explain further? After pondering for a day, I'm guessing the sealant in the assembly of the intake manifold can break down and cause air suckage. Nonetheless, I just need to ask y'all what's this all about.

Thanks! -Dan

 

[gator_rider2]

manual B1279 download it go to page 4 you see intake is 2 piece. The age sealant could leak.

 

[Hydriv]

One questions I have, though. Gator_Rider2 mentions I should "reseal the intake halves". Can you explain further? After pondering for a day, I'm guessing the sealant in the assembly of the intake manifold can break down and cause air suckage. Nonetheless, I just need to ask y'all what's this all about.

Thanks! -Dan

This is a notorious issue with the Onan engines. Time, heat and vibration cause the two piece intake manifold halves to leak air. Removing the manifold, splitting it open and then resealing it lis essential.

 

[Mr onetwo]

One questions I have, though. Gator_Rider2 mentions I should "reseal the intake halves". Can you explain further? After pondering for a day, I'm guessing the sealant in the assembly of the intake manifold can break down and cause air suckage. Nonetheless, I just need to ask y'all what's this all about.

Thanks! -Dan

This is a notorious issue with the Onan engines. Time, heat and vibration cause the two piece intake manifold halves to leak air. Removing the manifold, splitting it open and then resealing it lis essential.

I have just done this to 2 manifolds...made a big difference in how the Onan runs.I have a pdf file of this procedure that is very good.PM if you want and I'll send it to your email.I can't figure out how to attach a file like that to this reply.Make sure you do not use silicone to reseal the halves...E10 will eat it alive.I use Yamabond4 and Hondabond HT is also recomended, also make sure to get the new style intake gaskets...they are much better.

 

[Hydriv]

Just go to the members list LINK at the upper right side of your screen and click on it. Then find "Hilda's" name on the first page. Click on that. On the left side, you will have the option of sending PM's or e-Mails. Send her an e-mail with the PDF file attached.

 

[dhosler]

Got it. Don't know who "Hilda" is, but I just sent Mr OneTwo a PM.

An update to all: I have the manifold split, cleaned, and ready to put back together once I figure out (with Mr OneTwo's help) the proper sealant. Also, I have ordered a "valve grind" gasket kit, a brass float to repair my non-brass float, and a few other miscellaneous parts.

What an excellent forum. This is an addiction.

 

[Hydriv]

The products mentioned by Mr OneTwo can usually be found at your local Honda and Yamaha motorcycle dealers.



Hilda forgives you for that comment. :lol:

 

[Mr onetwo]

Just go to the members list LINK at the upper right side of your screen and click on it. Then find "Hilda's" name on the first page. Click on that. On the left side, you will have the option of sending PM's or e-Mails. Send her an e-mail with the PDF file attached.

Would Hilda like me to email that pdf so that it can be posted in the Onan folder of the tech section? :mrgreen:

 

[Hydriv]

Just go to the members list LINK at the upper right side of your screen and click on it. Then find "Hilda's" name on the first page. Click on that. On the left side, you will have the option of sending PM's or e-Mails. Send her an e-mail with the PDF file attached.

Would Hilda like me to email that pdf so that it can be posted in the Onan folder of the tech section? :mrgreen:

That was the idea. :lol: