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It's easier to drill two holes in your crank wheels to balance the crank.
Garbage Gaskets: Crank Case Too Tight
- Thread starter SEGACDX
- Start date
I ended up testing the engine yesterday and my god what a waste of time it was to even fix anything, last time I did this I got a lot of heat so much my engine would be burning hot everywhere on the bottom end. This time I just get a hot and useless engine.
I will have to get some gasket material and try these methods, thanks for the suggestions.
I will have to get some gasket material and try these methods, thanks for the suggestions.
Frankenstein
Deceased - Frankenstein 1991 - 2018
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- Jun 24, 2016
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Yeah hot and useless, that's what big daddy likes to hear.
Erm... Nevermind...
I did think that idea with hammering the cranks together was a pretty good idea, where does one buy those shims anyhow, I have a few left over from motors that have been cracked open but I don't know where to get them.
I also saw a motor with some very very bad play, like an 1/8th inch worth of slide between main bearings. It would actually push the thin crankcase seal out which is how the problem was discovered.
Jag is it me or is it possible to take just about any engine kit and make it greater than great, or is there a specific motor one would buy to make mods to.
For the most part it looks like they are almost all identical minus the variations for quality control.
Erm... Nevermind...
I did think that idea with hammering the cranks together was a pretty good idea, where does one buy those shims anyhow, I have a few left over from motors that have been cracked open but I don't know where to get them.
I also saw a motor with some very very bad play, like an 1/8th inch worth of slide between main bearings. It would actually push the thin crankcase seal out which is how the problem was discovered.
Jag is it me or is it possible to take just about any engine kit and make it greater than great, or is there a specific motor one would buy to make mods to.
For the most part it looks like they are almost all identical minus the variations for quality control.
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Steve Best
Well-Known Member
For shims I used regular steel washers drilled to the specific size I needed. You want a close fit on the journal.
I shimmed the wrist pin bearing as well. I needed a 16mm wide bearing and only had a 12mm, so put a 1.8mm washer on each side. Very important this bearing does not slip too far to the side. By taking a small diameter washer (M8 I think) and drilling it exactly 10mm I got the close fit, thickness and the small outer diameter I needed.
Yes, I think you can do a lot to improve these motors during a rebuild, without a machine shop.
This engine I am working on was a well worn generic and quite sluggish with a sloppy crank. Let's see:
1) trued crank, it was not bad but is even closer now, done with a hammer, tested with a dial indicator.
2) new seals and 6202 crank bearings (one journal was loose, punched and locktite to retain)
3) stuffed the crankcase around the bearing retainers and lower transfer port trough
4) oil flow holes to both crank bearings drilled
5) matched the cylinder transfer port to the case
6) new sealed 6202 bearings on the clutch shaft instead of the shielded grease leaking bearings
7) case halves cylinder surface matched by file and sandpaper (on a smooth surface) before crank installed
8) Lip taken off the inside edge of the transfer ports and small burrs removed, chamfered edges
9) new studs and 8.8 grade Allen head bolts installed everywhere
10) cut gaskets to fit intake and exhaust ports, trimmed case and base gaskets to fit
11) drilled muffler flange (and gasket at same time actually) 3/4" to fit the exhaust port
12) installed a crank seal retainer plate behind the stator coil (was missing)
13) installed a thinner sprocket so lighter 410 chain can be used
14) cleaned the burrs off the clutch shaft and push bar so it works freely and used waterproof grease
15) Cut a 3mm squish band out to 47mm on the head at the angle to match the piston
16) filed and sanded the head and cylinder flat (neither were) and set them up to a .8mm squish
All of these are significant improvements on what is essentially a stock engine.
I shimmed the wrist pin bearing as well. I needed a 16mm wide bearing and only had a 12mm, so put a 1.8mm washer on each side. Very important this bearing does not slip too far to the side. By taking a small diameter washer (M8 I think) and drilling it exactly 10mm I got the close fit, thickness and the small outer diameter I needed.
Yes, I think you can do a lot to improve these motors during a rebuild, without a machine shop.
This engine I am working on was a well worn generic and quite sluggish with a sloppy crank. Let's see:
1) trued crank, it was not bad but is even closer now, done with a hammer, tested with a dial indicator.
2) new seals and 6202 crank bearings (one journal was loose, punched and locktite to retain)
3) stuffed the crankcase around the bearing retainers and lower transfer port trough
4) oil flow holes to both crank bearings drilled
5) matched the cylinder transfer port to the case
6) new sealed 6202 bearings on the clutch shaft instead of the shielded grease leaking bearings
7) case halves cylinder surface matched by file and sandpaper (on a smooth surface) before crank installed
8) Lip taken off the inside edge of the transfer ports and small burrs removed, chamfered edges
9) new studs and 8.8 grade Allen head bolts installed everywhere
10) cut gaskets to fit intake and exhaust ports, trimmed case and base gaskets to fit
11) drilled muffler flange (and gasket at same time actually) 3/4" to fit the exhaust port
12) installed a crank seal retainer plate behind the stator coil (was missing)
13) installed a thinner sprocket so lighter 410 chain can be used
14) cleaned the burrs off the clutch shaft and push bar so it works freely and used waterproof grease
15) Cut a 3mm squish band out to 47mm on the head at the angle to match the piston
16) filed and sanded the head and cylinder flat (neither were) and set them up to a .8mm squish
All of these are significant improvements on what is essentially a stock engine.
Frankenstein
Deceased - Frankenstein 1991 - 2018
- Local time
- 12:52 PM
- Joined
- Jun 24, 2016
- Messages
- 5,035
By the lower port trough you mean the part circled in this image right?
And how do you drill oil holes for what bearings?
And how do you drill oil holes for what bearings?
Steve Best
Well-Known Member
Yes, those are the transfer port troughs. Here are the other details:
Steve
Steve
Right now I am in the process of making my own gaskets on the cheap, I am using thick paper folder as cheap test gaskets before I order some Felpro.
I took a measurement of the stock gaskets and they come out to 1/32" so I used 3 layers with one layer with adhesive to keep it all together. I hope for the best but will still be replacing it with good Gasket material, I guess I just wanted to see if I could and to get in some gasket making experience in there as well. If it works well I can use this method to make dirt cheap gaskets in a pinch.
I took a measurement of the stock gaskets and they come out to 1/32" so I used 3 layers with one layer with adhesive to keep it all together. I hope for the best but will still be replacing it with good Gasket material, I guess I just wanted to see if I could and to get in some gasket making experience in there as well. If it works well I can use this method to make dirt cheap gaskets in a pinch.
zippinaround
Active Member
A friend of mine said he used flexoid gasket material its oil and water resistant but not high temperature said it worked fine and is very cheap 1$ a sheet or something and comes in various thicknesses.
Steve Best
Well-Known Member
Paper and cardboard work well for base and carb gaskets on 2 strokes.
Temperatures are not that on the intake and case due to the cooling effect of the air/fuel mixture.
The main thing you need is sufficient softness for surface defects and resistance to fuel and moderate heat.
You can test the effectiveness of your gaskets (or sealant) by pressurizing the case (plug the intake and exhaust) to 5-7psi (use a bike pump only, or you will blow out your crank seals) and checking for leaks.
Steve
Temperatures are not that on the intake and case due to the cooling effect of the air/fuel mixture.
The main thing you need is sufficient softness for surface defects and resistance to fuel and moderate heat.
You can test the effectiveness of your gaskets (or sealant) by pressurizing the case (plug the intake and exhaust) to 5-7psi (use a bike pump only, or you will blow out your crank seals) and checking for leaks.
Steve
I did end up making good gaskets with my paper folders but it is still not good enough for my whiny baby of an engine so I ordered some Fel-pro sheets in a set of 4 types for $11.74 on amazon. I will use the 3/64" or 1/32" or may even try out the thicker 1/16" and 1/8" for other things. I've looked into crank types and have found I am not the only one to notice the difference between the ZAE-50 and FM-80 cranks.
I find it very annoying that the ZAE-50 Crank is not only bigger then the older FM-80 but the crank case is only slightly bigger but not enough to have good clearance.
Even when using a 1/32" stock gasket it still rubs a bit causing heat, powerless and wear on the engine.
All I expect is the newer engines made now to be as good as the FM-80 but I still cannot believe this is even a problem in the first place. You could install the crankcase with only RTV and it would hold up so well I would never need to worry about leaks for a long time.
I could have just got a lemon but I have more then one crankcase with the same problems so this could just be a overlooked problem.
Anyways I am going to try to cut some gaskets and get my worthless engine working properly.
Here is the thread and an image from it that show how much bigger the ZAE-50 Left and FM-80 Right really are.
http://motorbicycling.com/showthread.php?t=57810&page=6
I find it very annoying that the ZAE-50 Crank is not only bigger then the older FM-80 but the crank case is only slightly bigger but not enough to have good clearance.
Even when using a 1/32" stock gasket it still rubs a bit causing heat, powerless and wear on the engine.
All I expect is the newer engines made now to be as good as the FM-80 but I still cannot believe this is even a problem in the first place. You could install the crankcase with only RTV and it would hold up so well I would never need to worry about leaks for a long time.
I could have just got a lemon but I have more then one crankcase with the same problems so this could just be a overlooked problem.
Anyways I am going to try to cut some gaskets and get my worthless engine working properly.
Here is the thread and an image from it that show how much bigger the ZAE-50 Left and FM-80 Right really are.
http://motorbicycling.com/showthread.php?t=57810&page=6
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