OS FS-52 Timing

[Andy J]

Onto my next issue today with a newly acquired FS-52 which was not a good buy no prop nut and stuck valves.  Whilst I did manage to get the engine running several days ago found this morning I had zero compression and on inspection noted zero movement on the inlet valve.  Removed the rockers and found that there was also zero movement on the inlet push rod so opened the cam housing and found considerable amounts of brown gunge inside which I have now cleaned off the two bearings and cam followers. Quick re-assembly and all seems ok so I know the mechanics of the valves are now fully functional.

 

The issue I now have is which way round should the cam lifter be inserted and what position wrt the piston should the exhaust cam be to correctly time the engine?

 

[Engine Doctor]

Hi Andy. Look at the cam shaft drive cog . you should see a punch mark on one side . The shaft is inserted with this facing out. The punch mark should align with the center of the the bottom of the outer cam follower when fully inserted with engine set at TDC. When inserting the cam shaft will turn as it engages with the crankshaft so allow for this when lining it up. A quick final check that the timing is correct it to check the as the engine turns over TDC that the valves are " on the rock" One closing and one opening .

Have you removed and cleaned the cam followers ? If not I strongly suggest you do as any gunge or corrosion will quickly re establish itself and cause the problem again. Also check the valve springs for corrosion as they often snap and cause the valve not to close properly 

[Nigel R]

If it's really gunged up you may not be able to see the punched dot.

 

I'd clean up the cam as well, if it's all gunked up in there, while you're doing the followers and valves and springs.

 

[Andy J]

Thanks, just watched a video on youtube of a 52 reassembly but the audio was not clear on the point the cam gear is inserted.

 

Just to confirm the dot is at the top and should align to the push rod with the piston at TDC.

 

Gunge is now fully cleaned off the cam followers, most of it was on the bearings. Will also check the springs.

 

 

[Andy J]

No obvious damage to springs so did a short test run  which it passed with flying colours. Little compression after the test run so suspect the piston ring could do with a clean up also so may consider a full strip down of the engine given the amount of crud that came out of the cam gear.

[Nigel R]

Maybe the ring is just freed up now? Sometimes ringed motors offer little resistance when turned by hand, but when up to speed the ring is pushed out and does the business.

[Engine Doctor]

The OS should have reasonable compression. You say a lot of gunge came out of the engine. Brown gunge in glow engines is not good and usually indicates rusty bearings,if that's the case it sounds as if it needs a proper overhaul. If the piston ring is stuck in the piston groove it can cause  damage to the piston and liner. Also any rust in the bearings will allow the crankshaft to camshaft tolerance change affecting the valve timing lowering performance not to mention the total failure of the bearings causing serious damage to engine; not to mention the rust particles grinding away at the moving parts. If you do change the crankshaft bearings don't forget to also change the camshaft bearings.

[Andy J]

Certainly the crud was brown in colour but came off easily with cellulose thinners although the residue appeared to leave tiny specs of brown substance in the fluid when brushed off with a small paint brush. Could pour some thinners into the piston and crank and let it sit overnight.  Little reluctant to open the engine up given my bad experience with the RCV 58CD bearings.

 

Out of interest what size bearings does the FS-52 use?

Edited May 21, 2021 by Andy Joyce

[Engine Doctor]

Hi Andy  off hand can't remember size of bearings but simple to  measure . You can also look at Model fixings site as they list bearingby engine make and size.

 

Soaking with thinners will only remove some of the gunge/rust that's obvious but nit where it matters.

[Manish Chandrayan]

MR 6001 C3 for the rear bearing . If you get the sealed or shielded ones remove the shields or seals. Front bearing being MR 608 2RU C3 . Remove the rear rubber seal .

MR 695 x 2 for the cam bearings   

Edited May 21, 2021 by Manish Chandrayan

[Martin Harris - Moderator]

It might be burnt castor residue but in my view, it's a false economy not to change the bearings and it's more likely to be rust anyway.  I've found that even if you free up ball races which have been clogged with dried castor, some skidding will have resulted and caused microscopic wear which will soon get much worse with some running.  Left for any length of time, the bearing cage will probably fail and at this point, loose balls will cause havoc within the engine.

[Martin Harris - Moderator]

Just spotted Manish's post.  It mentions C3 in the specs and for clarification, this denotes bearings with increased clearance intended for high speed applications in hot conditions.  Sounds familiar to me...

 

You might notice that there's slightly discernible play in these over and above that in standard bearings but this is by design.

 

Jon Harper would perhaps be the best person to comment but I've used these larger clearance bearings (where available) fairly extensively.  I don't know what specification manufacturers or specialist firms like Modelfixings supply and it's something that I'd be interested in hearing informed opinions about.

[Manish Chandrayan]

Martin, my go to reference for bearing sizes is Boca Bearing in US. I pick up the sizes and specification from the website and then buy the bearings locally. 

If you refer the page they have various options where in the economy option they recommend C3 fit for the main bearing but normal fit for the front bearing. While the higher performance (and costlier) option recommend C3 fit for both  

Edited May 21, 2021 by Manish Chandrayan

[Glenn Philbrick]

The bearing sizes that are quoted above are correct. If you are going to change them you will have to remove piston and liner don't forget to mark these so they match when you put them back. It really is an easy engine to overhaul so good luck.

[Andy J]

Thanks all, will order up a set of bearings so as to at least have them to hand if I go ahead with a strip down.  On the cam gear bearings how would one remove the existing bearing as suspect this is difficult given the casting it sits in is sealed at one end.

 

Also out of interest when I changed the bearings in the RCV engine a couple of weeks ago I noted one bearing had a metal cage. What is the suffix code that ensures the bearing has a metal cage as would have thought this would have been preferred against the plastic type.

[Glenn Philbrick]

The cam gear bearing will come out when you heat the crankcase up which you will need to do to get the larger crankshaft bearing out. They can be a bit stubborn so a wooden dowel that is a tight fit in the centre is one way to get them out.

 

[Manish Chandrayan]

Wooden dowel as suggested will work. If you are feeling bit indulgent you can always buy proprietary bearing removal/installation tools. Otherwise if the bearing is still stubborn there is wax trick. You basically keep forcing more and more wax through the bearing center. Eventually that wax moves under the bearing races and forces the bearing up. 

[Andy J]

Like the idea of wax Manish as being a bee keeper I have plenty of wax.

[Rich Griff]

Can you post a picture of the engine to show where the bearings still, in a blind hole.

 

I very recently removed the inner bearing on a merco 61, after several cleaning/ flushing cycles.

 

I set up an old sauce pan on a camping gas cooker to heat sufficient oil to dip the c/ case in to heat up and expand it.

 

The rear of the c/case has a handy flat surface. I dipped the c/case into the hit oil so that the case was deep enough to cover the bearing area, and counted to twenty.

Removed the casing covering the hand hold with rag and brought down the casing squarely onto a but of flat wood.

 

The bearing came out first strike with no drama's.

 

Momentum and transfer of energy....a gravity/kinetic hammer ?

 

The rear of the bearing and where it fits had quite a lot of goooo' and gunge, even after lots of cleaning.

 

Further cleaning was then easy and enjoyable.

 

Awaiting reply from model fixings.....

Edited May 22, 2021 by Rich Griff

[Manish Chandrayan]

Cheers! Andy

But I am sure you will try the tight dowel first

 

Rich the heat and inertia method will work for the case bearing as there is space for the bearing to move when the case is suddenly brought to a standstill.

In case of the cam cover bearing the bearing is almost flush with the housing.     

[Andy J]

22 hours ago, Manish Chandrayan said:

MR 6001 C3 for the rear bearing . If you get the sealed or shielded ones remove the shields or seals. Front bearing being MR 608 2RU C3 . Remove the rear rubber seal .

MR 695 x 2 for the cam bearings   

Manish what does the 2RU designate on the front bearing as cant find that suffix code on the simply bearings site?

[Andy J]

Believe 2RU is 2 rubber seals according to the Boca Bearing site.

[Manish Chandrayan]

14 minutes ago, Andy Joyce said:

Believe 2RU is 2 rubber seals according to the Boca Bearing site.

Yes like ZZ is two metal shields,  while RU is rubber seal so 2RU becomes both sides sealed 

[Manish Chandrayan]

47 minutes ago, Andy Joyce said:

Manish what does the 2RU designate on the front bearing as cant find that suffix code on the simply bearings site?

I suggest to call up Simply bearing and check as they only mention the bearing sizes and not the other specs like fits, seals etc .

Best to check the specs from the original bearings 

 

Apologies, I was mixing up Simply Bearings with Model Fixings 

Edited May 22, 2021 by Manish Chandrayan

[Manish Chandrayan]

This document will explain at length the bearing nomenclature system. There will be differences between manufacturers to some extent