I don't know how to call it in English...I do my best...I speak here German all the time, and my mother tongue is Spanish =)

Also...you take the bearing...it has an outer ring and and a internal ring...the balls are keep between those rings... The crankshaft goes through this internal ring. Where the seal meets this internal ring..it is only rubber there, elsewhere the seal is brass covered with rubber....


Maybe an image is better =)

Just removing the seal was not a good Idea to me because front bearing is not sealed and I didn't changed the bearings....it put lot of oil in the cowling...much more than a bushed engine puts there...

Why not just put a big glop of grease on the cam?


Ed Cregger

Would it work even on the bronze bushings? that's where I had the failure, not on the tooth...that's why I think oil will do a better job than the grease??

GK, I wonder about removing the seal completely as the crank vent on the rear of the back cover keeps the crankcase ventilated. estradajae, did you consider removing the seal completely??

I already posted that...

at first I took the seal completely...but I got lots of oil coming from the front bearing.

If you use a front sealed bearing it may be the best solution though, removing the seal in the rear bearing.

Many, many, engine were made just that way. The small OS four strokes continue to be made that way. It will do no harm, just allow plenty of oil into the cam box.

I wanted permanent solution. Grease would need occasional topping up. If fuel did get in there you'd have to be sure the grease was compatible with the fuel and lubricants.

gkamysz, what led you to remove the seal in the first place? Did the motor start giving you problems, and now that you have removed the seal does it get messy or is it normal?

I wasn't going to wait for problems to occur. It was a bad design. There simply was no intentional means of lubricating the cam box. It wasn't my engine and the owner now has it. Here is my original post:

http://www.rcuniverse.com/forum/m_87...tm.htm#8788355

Like I said many engines were built at the factory with open main bearings and shielded fronts. I have put sealed bearings in the nose of some of my other engines, but that was for a different reason. www.dieselrc.com/project1.html

gkamysz, ok thats some good info, so what do I need to do to remove my seal to get lubrication to the cam? Do I have to remove the bearing to do this?

With everything out of the case but the cam and the crankshaft; remove the camshaft. Note the timimg mark when the Crankshaft pin is at TDC. It will either be stright up or down. Maybe 5* off. Just make sure the crank pin is at TDC. Remove the cam. The gears are helical shaped so it will reuire a little rotation. Remember that when reassembling. Now you don't have to pull the bearings. remove the crankshaft. yoiu now have an exposed seal. Using a small angled pick hook into the seal and pull it out. reassemble the crank and motor.

i plan on removing my seal and drilling two holes 180* aprt through the metal part of the seal about .020" each and try that. I want the cam lubricated bot don't want the cowl soaked in oil.

The first pic is of the case and there is not noticable oil supply to the camshaft

I put the case with the bearings on a small cookie sheet in the oven @ 275* for 20 min. Rear bearing fell out when I tapped the case against a cutting board. careful not to hit the cylinder fins. The front bearing I pushed out with a butchers steel. Hey, I was in the kitchen and didn't want to run downstairs for a dowel.

Picture of the sealed rear brg and the front bearing covered

Picture of the pick I used to pullout the seal

Removing the seal
"
Back of the seal. I will drill from this direction to minimize burrs into the brgs. twoi .020" holes will not pass as much as one.040" hole so I will increase the size to .025"

My concern with that is that oil will tend to sit in the cam box. If it's not flushed well it will lead to corrosion. I prefer good flow in and out of all parts of the engine.

The corrosion part is not completely true. It depends on the oil you use.

Yes, Of course. unfortunately I've seen so many corroded engines that I don't think fuel is too much of a factor. I will say that engine with a green tint to the insides are usually much worse.

I don't know if it would be "the best" solution, but it would have to be better than what is happening stock out of the box. Then again, is anyone having wear problems? Or is everyone just reporting a lack of obvious lubrication, but without any wear trouble? The engine is new to me, so I'm not aware of hearing of any actual wear problems. Anyone?


Ed Cregger

Ed I actually have wear on the cam bushing, on the bushing that is inside the engine, not in the one that is on the cam cover. It wore but was slight, and the result was like if I had drilled the top of the bushing with a drill a size bigger 1mm deep, the cam is still being well supported there and without play... but it was indeed a failure I think....it was a big surprise when I found the crank spiral full of bronze powder.

Jorge

I guess that answers that question.

Thunder Tiger impresses me as a company that cares about its reputation. Even if they are temporarily at a loss for words. I wouldn't give up on them just yet.

I still think that a dab of grease might not be a bad idea in both left and right side bushings and the gears. As to which kind of grease, I'm not sure.


Ed Cregger

I'm still waiting for the answers....
I'm impressed that Thunder Tiger Europe haven't said anything!! and the guy in Taiwan didn't answer again.... Now I don't know what to expect....I have my engine running right anyway.

Jorge

Just picked up one of these engines and found this thread... I was reading the instruction manual and Thunder Tiger recommends 30% oil?!? Does this seem excessive? I checked the Cool Power 4-stroke blend and it contains 20% oil. Other vendors have similar amounts of oil in their blends. By comparison, my OS Max .91 Surpass recommends 18% oil. What gives? - are you adding extra oil or using a different fuel?

This thread is most interesting. I have an older TT 91 and a 54 that both have the crank breather on the bottom of the case beneath the helical crank/cam gear as opposed to being on the backplate. On the 91 there is a very tiny passage drilled from the crank case (just above the main bearing seat at 12:00) through to the cam bearing housing. I'm not sure about the 54. To the best of my knowledge neither have shielded main bearings let alone sealed. With the vent forward of the main bearing, gases and subsequently oil, will get to the cam gear and front bearing. All is good and fine except the 91 has such little blow-by that nothing much at all comes out of the breather. I simply oil it now and then - no big deal.

Being that the vent on the 75 is behind the main bearing would indicate no lube is getting to the front end. I agree: design oversight. Other than replacing bearings or altering them it may be possible to drill a .015 - .020" passage hole to the cam gear housing as is done on the 91. If the front bearing is not sealed, as stated in other posts, this could be an excellent lubricating means.

I understand most people are reluctant to make such a modification but it may be possible to do fairly easily.
Just thought I'd offer something different.

Drilling a passage is easier said than done. First, try to find a small drill long enough to reach the area you are trying to drill!! Removing the bearing seal is the easy solution. While you have the crankcase hot to remove the main bearing if you are worried about a wet nose, just replace the front bearing with a sealed unit.

The 30% oil is a mistake. The regular 18% is just fine.

Yep Greg, that was my concern as well. It may be possible with a dremel or a pin vise. I haven't tried it yet or looked into it further. It remains an option.

Replacing the front bearing with a sealed bearing would rely on gases being able to pass through the cam unit to find an outlet at the push-rod tube ends, valve cover, or down the valve stems. Without an outlet, the gases will not effectively pass through to the front end.

The valve train gets plenty of oil without any mod, so I would say, you don't need anything to do there. But I would say that a sealed front bearing and a shielded (or without shields) rear bearing is all we need here, this way cam gets plenty of oil and the oil wont be expelled through the thrust washer.

The pics here are when the engine was new, the cam picture shows just a little dark oil on the walls, but not enough to lube the thing.

Saludos,

estradajae, do you have pics of the same areas after poking a hole in the main bearing seal? I'd be willing to bet the oil residue is much less dark. Once the engine is well broken in the oil should lighten up anyway.
I'm not at all thrilled with dark oil. The oil that comes out of my 54's front mounted vent is pretty clear and the cam unit does not have dark oil in it.
I just checked with one supplier and longer than standard #76 bits are not available to the best of his knowledge. A pin vise might work.