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Alberto Hirsch

Bearing for ohlsonn 1hp

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I'm a little confused too, are you missing a bearing or do you what to replace a damaged one?

There are several different bearings used for the crankshaft, PTO shaft, con-rod & gearbox (if fitted) and different sizes with the various design changes made to these engines over the years.

Some pictures may help identify which bearing you need.

 

David

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Good evening,

 

I'd like to replace the bearings that are broken or parched. I have doubts about which engine model is correct, so follow some photos.

 

I also need the carburetor diaphragm.

 

Thank´s.

 

 

 

P_20171215_211502.jpg.7562b481fc14f09b24c08a5ec4642719.jpgP_20171215_211338_SRES.jpg.7bab4a760c995f3d89a3507e3a268a03.jpgP_20171215_211219_SRES.jpg.389c49ba18aa722b959e205d5a29382d.jpgP_20171215_211103_SRES.jpg.90371a6480ef198485e33e9843fe41e8.jpgP_20171215_214456_SRES.jpg.ac86d810d21a8ef5e04d0774884a3c56.jpg

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From the pictures that you have posted, I can tell that your engine is an earlier production 3/4HP one (Mods please correct the title) as it has plastic bearing cages for all the bearings & the metal reed valve, it will have been made before October 1963.

Oddly the carb has the updated quadrant speed control but not the primer button (maybe the bottom half of the carb has been replaced at some point).

 

See the NIAE report from 1964 for more information on some of the problems they had with these earlier O&R engines & design changes introduced then. I have recently added a PDF of the report to the thread here;

The last couple of O&R engines I have rebuilt have also been earlier ones with the plastic bearing cages. As they are much harder to find replacement parts for, I reused the bearing cages with no cracks and had to borrow some from an incomplete parts engine of similar age (which I also discovered someone had previously robbed the con-rod bearings & cages from) to complete the restoration.

 

I really need to identify and dismantle a 1964 engine to find out if the updated steel caged bearings can be used for the earlier engines, as I have quite a lot of them in my collection. I do know they increased the size of the crankshaft main bearing at some point in the later 1HP compact III engines.

 

David

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Didn't need to take anything apart, all the information needed was in the various parts diagrams & manuals I have.

 

The bearing assemblies used in the 3/4 HP early engines dating from 1961 (after s/n 006072) to Dec 1963 are;

A-27-2 (2 sets) used for both back-shaft (PTO) bearings, can be replaced with A-27-18 according to the 1971 price list.

A-27-3 used for crankshaft outer (flywheel side) bearing, part number stays the same after 1964 & 1965 for steel caged version.

A-27-4 used for crankshaft inner (main) bearing, can be replaced with A-27-17 according to the 1971 price list.

A-27-11 used for con-rod big end bearing, can be replaced with A-20-5-13-7 according to the 1971 price list.

 

I would be interested in seeing pictures of NOS steel versions of A-27-2, A-27-4, & A-27-11 as well as the later replacements A-27-17, A-27-18 & A-20-5-13-7.

Send a PM to Webhead to see if he has any of the bearings needed to replace the damaged ones, as well as a replacement carb diaphragm. I will enquire to see if he has any spares remaining afterwards.

 

David

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Hi Alberto

 

Click on the envelope symbol next to your username at the top right of the page to start a PM, or hover the mouse cursor over Webhead's name in post two & click the message option.

 

David

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Ok, I cleared out my message box. Not sure if I can help with the bearings, because as David said, I do not know if they cross. I might have an old used crank housing,

but I'll have to look. I do have diaphragms.

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I remembered that the pile-o-bits Tiny Tiger I restored came with a couple of NOS bearings, mostly of the wrong type for it.

 

Here is the crankshaft (flywheel side) bearing part number A-27-3, the rollers are not with it as the packet had been opened, this isn't the first time I've come across an updated part with the same part number as the original part.

 

SAM_0011a.jpg.1856d1f4c6c79bd1533396936a1abd0b.jpg

 

I should point out that the steel bearing cage is very slightly thicker than the plastic version, here are the two together.

 

SAM_0012a.jpg.636455f894f0f8f7617eb353c26589af.jpg

 

Here is part number A-27-1, this was incorrectly ordered by a previous owner of the Tiny Tiger, this bearing was only used in the first 6000 (approx) engines produced. It is also used in gearboxes for all the 3/4HP, 0.85HP & 1HP engines.

 

SAM_0007a.jpg.72e6d8221587ba6be17a288c2f57fd19.jpg

 

David

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Well, I have the diaphragm along with many bearings, but I do not have the plastic housings or the time to figure out if they cross. Not sure how to help you.

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I've been checking some if some of the steel caged bearings can be fitted to the older engines that used the plastic caged bearings, using the crankcase from the incomplete parts engine (s/n 044706) that donated some bearings for the Tiny Tiger Model 400 restoration.

 

SAM_0027a.jpg.8c3305443857e21859d99ea2788a768a.jpg

 

Here is the outer crankshaft (flywheel side) bearing (part A-27-3), the steel caged type fits fine.

Note the service manual states that the closed end of the cage should face outwards, as I didn't want the rollers to escape when removing it I put it in the wrong way up.

 

SAM_0031a.jpg.6c92e435636c03ac95b4c26226de5b50.jpg

SAM_0030a.jpg.cfc6b4980532ba905bbc18de23ed21f7.jpg

 

Here is the inner crankshaft (main) bearing (part A-27-4), as I don't have any of the double steel caged bearings in my spares, I used the only two single ones I have for this check, they also fit OK.

At this point I noticed the larger plastic bearing cages from the Tiny Tiger 400 have shrunk making them a force fit, not good for a bearing at all!!

I can't check possible replacement part A-27-17 as I don't have any.

 

SAM_0032a.jpg.78143992aee393f79cb86e7e0cc6bc60.jpg

SAM_0033a.jpg.0a5f98ba825b2f8742f0a9d583ee61ad.jpg

 

Here are the back shaft (PTO) bearings (part A-27-2), two sets of these are used but I have only pictured one set.

They do fit, but could benefit from the burrs being removed before use.

Note the slight difference in thickness of the steel caged ones (I'm not sure if my spares are the single types intended for use in the gearboxes as the rollers are not in them).

I can't check possible replacement part A-27-18 as I don't have any.

 

SAM_0036a.jpg.3f5c2afe2a4ccbd8837b154ac25645ce.jpg

SAM_0035a.jpg.149a933392fa22c73215c2dffe00d9b6.jpg

SAM_0037a.jpg.54f36b34cd8f3c383d9e4c0ed4a76b12.jpg

SAM_0034a.jpg.c79b734254f57708a29aee1193e779f0.jpg

 

This leaves the con-rod (big end) bearing, unfortunately I don't have any of either the plastic or steel caged (part A-27-11) or washer retained (part A-20-5-13-7 ??) bearing types to check this one.

I suspect the missing bearing from this crankcase was the steel washer retained type, as one washer is still in place.

 

SAM_0038a.jpg.2593e2706b16e06cfe4ad3dd51fc7e2f.jpg

 

Here are a couple of pictures of the con-rod (big end) bearing in a different 3/4HP engine (s/n 074258), I only took the induction/PTO housing off this one (they also have the plastic caged bearings fitted). The con-rod bearing is the steel washer retained type, could this be part A-20-5-13-7 ??

 

SAM_9991a.jpg.752f3a831bf2b4a31e4e3bf92043c1be.jpg

SAM_9989a.jpg.faebdba0cf4e474b4272ea8f2739f37e.jpg

 

I hope this can help with identifying suitable replacement bearings for your engine.

 

David

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30 minutes ago, Webhead said:

Once again, thank you David, for doing some of the footwork.

 

It's a task I had been putting off for a while, as I have some spare later bearings (possibly NOS but without the packaging and all mixed together) I needed to identify and I also wanted to work out what I may need for restoring some of the other early engines & tools in my collection.

 

David

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Dear,

 

Sorry for the delay in the return, but with the end of year period things get a little complicated for me. It would be possible for you to send me the bearings you have and the diaphragm. It would help me greatly in restoring this engine. If there is any cost, let me know how I can send it to you.

 

Right now, I appreciate the help.

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