twoturnspin

Hi,

I've got most of OS 70 Surpass 4 stroke engine apart but have two issues currently:

1. Can't get the con rod off the crankshaft. I have removed the linerand can get con rod about half way off the crankshaft but no further. I was concerned about damaging the copper bushing that lines the hole in the con rod and so didn't want to lever it off too hard. Any ideas here? There just doesn't physically seem to be enough lateral movement of the con rod to allow it to get all the way off the pin.

2. I got the cam shaft out but slipped and are now unsure as to the exact position it should go back relative to the crankshaft location. How do I get the location and therefore the timing right?

Any ideas?

Simon

Bax

My Feedback: (11)

Please check to make sure the connecting rod is getting all the way to one side of the piston. Sometimes burned fuel residue will accumulate next to the connecting rod on the wrist pin. This would prevent the rod from sliding all the way on the wrist pin. Also make sure the crankshaft is fully forward. Sometimes it can slip aft when you're disassembling the engine. Finally, you can use the nose of curved needle-nose pliers to pry a little bit. This is normal on many engines.

The camshaft is set so that the dot on the side of the cam gear is in direct alignment with the cam followers and pushrods when the engine is at Top Dead Center. You can download the diagram from the O.S. website.

twoturnspin

Thanks Bill, much appreciated. I also got advice that I should remove the pin that holds the piston and con rod together, what do you think?

Simon

twoturnspin

Hi Bill,

Just two more questions:

I was advised that the correct bearings are a 6002Z and a R6Z. Looking at the rear bearing I found that it was marked as a 16002Z. Can you advise what the correct number is, I can't find a reference on the OS site.

Do I align the timing mark on the cam shaft between the centre of the cam shaft and the point where the cam followers & push rods join or do you mean something different ie. the point where the cam follower touches the cam shaft? I couldn't find a diagram on the OS site the shows the alignment.

All the best,

Simon

Bax

My Feedback: (11)

We'd not have the specification you're looking for. We'd only have the O.S. stock numbers:

OSMG3060 26731002 FRONT BEARING 40-240
OSMG3116 45630000 REAR BEARING FS61

For timing, here is the FAQ:

http://www.osengines.com/faq/product-faq.html#q15

We're sorry, but we thought the diagram was on the web. Please send an email to us for the diagram.

twoturnspin

I've sent you that email Bill, thanks for your help here.
Simon

twoturnspin

Hi Bill,

Sent that email a while back but it may not have reached you, thought I might post it here to help.

[email protected]

Are you able to send the diagram to me please.

Simon

Bax

My Feedback: (11)

It's been sent.

twoturnspin

Thanks Bill, received diagram just fine. Your support here much appreciated.
Simon

cheli

I need help with the 0s 70 surplus as well. My fuel tank has two lines coming out and the motor has two nipples plus one on the muffler. I understand the one with the clunk goes into the carb and I assume the other goes into the nipples on the top but how do I route one to the muffler?

Bax

My Feedback: (11)

The nipple on the muffler is used to pressurize the fuel tank. That's routed to the vent line in the tank. The other line in the tank is the fuel pickup and is routed to the carburetor.

The third nipple is the crankcase vent. You just route it overboard...usually through the bottom of the cowling.

rctrax

I have found on the os engines I have had apart that you must take the wrist pin out of the piston/con-rod to get the rod off the crank. There is a hole that you can align with the pin then insert a small drill or simalar tool into the pin and work it out and then the piston can be removed, then the rod.

Campgems

Bax, hope yo catch this quickly. I'm pulling apart a 70 four stroke that went into an stock pond this morning. It belongs to one of the young guys at the club, and he has not engine repair experience. Luckly, there was no damage to the engine other than it was full of water. The piston and rod are clean. I was afraid it hydro locked and blew the rod as it was running well above mid range when it went in. I've run into two things I need to run by you before going any further.

Wrist pin. I am guressing that a long #2 wood screw or the likes that will go through the wrist pin and screw into the teflon end is the way to remove the pin. I don't want to pry on the rod to free it from the crank. Am I on the right track with this?

Cam Bearings. I am guessing that you would pack the cavity with grease and tap in a sutiable size rod to use the grease to push the bearing out, like a pilot bearing on a car crank. Again, am I on the right track here.

I need to pull every thing apart to clean the water out. I expect the cam bearings and the front crank bearing have water trapped behind the seal and should be removed and cleaned. I may just replace these three, but the issue of removal is there in any case.

Thanks for an answer in advance.

Don

Campgems

I got the engine apart, cleaned and re-lubed and back together. I used a drywall screw that I ground down the OD on until it fit inside the wrist pin, but still had the sharp tip. That bit into the teflon tip and allowed me to pull the pin.

I decided not to pull the cam bearings and front bearing. I just soaked them in a beaker of fuel for an hour or so to absorb any moisture trapped behind the seals. I the soaked them in a bath of Castor Oil and reassembled. This should be OK. the engine didn't have many hours on it and looked new inside.

I still have the question on how to remove the cam bearings from the crank and bearing cap.

Don

Bax

My Feedback: (11)

We remove the bearings by heating the case. The aluminum case will expand more than the steel, and the bearings will usually fall out when we rap the case against a block of wood. The bearing in the cap will usually just fall right out.

You removed the wrist pin the same way we do, but we usually use a bent pin to stick into the hole of the teflon bushing. We then use an easy-out to grip the metal wrist pin. That usually slides it right out. Sometimes, only a piece of bent wire is needed to slide out the steel wrist pin.

Campgems

Thanks Bax.. Good info to keep in mind for the next time. I'm sure they arn't draining the pond next to our field anytime soon, so I may get another shot at rebuilding one, though I hope not.

Don