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Hi all,
After measuring my valve clearance with a feeler gauge the exhaust cleanse is under at .006” (spec is between .007-.009”).
I couldn’t get a good reading on the intake side because it was so tight (spec is between .005-.007).
My question is how critical is it to have a gap? And what problems could I possibly encounter with too tight a clearance?
Regards.

The main issue is the valves may not close all the way causing valve floating and loss of compression, low power, hard to start.

The lessening gap is caused by heat warping the block and the valve seat area is coming back slightly. You need to remove the valves and grind the stems a hair until they are back in spec, or the heat/warping will just accelerate.
I wouldn't worry about lapping or anything like that, as it would take regrinding the valves and seats to correct the warp.
Removing the valve springs can be tricky without the proper tools, but look on youtube, you will likely see some good ideas {and many,many chitty ones}.

Made removing L head valve springs alot easier, https://www.amazon.com/gp/product/B001OK9TRK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Thanks for the replies.
I ground the stem down using some sandpaper, lapped them in and reinstalled them (using cable ties - a trick I saw online but definitely want to invest in the actual tool).
Then after installing the head I realised the springs are in the opposite orientation (one has the tighter side on the bottom while the other on the top ?), Is there a correct orientation? And does this matter much ?
Regards.

The closed coils go to the bottom .
Now it does make a difference on a motorcycle engine doing 8000 rpm.
wether it is significant on a side valve mower engine running at 3500 is a different matter & i doubt if it would
The open coils at the keeper end would make the engine easier to assemble & I suggest that is why they use a progressive spring.
It also prevents resonance in the spring but again at mower speeds I can not see that being a problem.

Thanks [B]bertsmobile1[/B], I ended up correcting the orientation of the valve springs.

So after assembling my 4 stroke B&S mower engine (Model 95902), I noticed the flywheel isn't rotating smoothly by hand.
It's easy enough until I get to the intake stroke then it gets stuck and requires more force.
I compared it with my dad's mower and his one rotates smoothly with momentum throughout!
After some research online, I found the problem could be:
1. not enough valve clearance
2. over tightening of the connecting rod cap

Does anyone have any other suggestions or could there be other causes?
Has anyone encountered a similar problem before?

Regards.

What was your final valve clearance reading?

Exhaust = .0035"
Intake = .006"

I also overfilled with engine oil which i plan to drain later but didn't think that would affect the operation.

https://kapwi.ng/c/h2E2RsQR

Hi again, the link above shows a video of me trying to rotate the flywheel and you can see how it’s getting stuck.
I know my valve clearance is out but I didn’t think it could create this problem?

I’m thinking to grind the stems again to get the clearances to spec but am wondering if there is a deeper issue here?

Any ideas/ suggestions?

An overtightened big end will be tight period, not go tight then loose unless the journal is very oval .
a bent rod can cause tight loose situation.
Is it the same plug in as plug out ?

bertsmobile1 said:

An overtightened big end will be tight period, not go tight then loose unless the journal is very oval .
a bent rod can cause tight loose situation.
Is it the same plug in as plug out ?

Click to expand...

Yeah it’s the same with the spark plug in and out.
I am going to check to see if the flywheel key is still ok.

The valve spings get compressed and that will cause a resistance to rotation
MArk where the tight spot is on the flywheel and see if it is the same every revolution or every second revolution.
A con rod / piston problem will happen every revolution where as a valve cam type problem will be every second revolution.
If he seats have ben cut too deep & too much take off the valve stem or the valves are not seated properly the valve spring can bind
so watch the valves while rotating the engine as by hand as well .

bertsmobile1 said:

The valve spings get compressed and that will cause a resistance to rotation
MArk where the tight spot is on the flywheel and see if it is the same every revolution or every second revolution.
A con rod / piston problem will happen every revolution where as a valve cam type problem will be every second revolution.
If he seats have ben cut too deep & too much take off the valve stem or the valves are not seated properly the valve spring can bind
so watch the valves while rotating the engine as by hand as well .

Click to expand...

I just finished draining the oil and have disassembled the fuel tank and muffler.
Will try what you’ve suggested @bertsmobile1 and let you know how it goes.
Thanks.
Regards.

mmoustafa said:

I just finished draining the oil and have disassembled the fuel tank and muffler.
Will try what you’ve suggested @bertsmobile1 and let you know how it goes.
Thanks.
Regards.

Click to expand...

Hi all,
So I tested the mower last night and it was much smoother this time - at least it wasn’t getting stuck anymore.
I’m thinking it was getting stuck because I overfilled it with oil and this was creating additional resistance? Could this be the case?

The valves were moving smoothly but I also re-measured the clearances:
Intake = 0015” (spec is ~.008”)
Exhaust = .008”

I could see a faint spark when turning the flywheel by hand. I then tested the magneto with a multimeter and was getting 2.9 kohms (low end of the acceptable limit).ould this be causing ignition problems?

Lastly, how freely should the flywheel spin? Is it normal when turning the flywheel for there to be more resistance during certain strokes? Should the flywheel spin a little on its own when I give it a turn?

Much appreciated.
Regards.

You need energy to compress the springs on the valves so it should spin freely till the springs start to compress if there is no spark plug fitted .

mmoustafa said:

Hi all,
So I tested the mower last night and it was much smoother this time - at least it wasn’t getting stuck anymore.
I’m thinking it was getting stuck because I overfilled it with oil and this was creating additional resistance? Could this be the case?

The valves were moving smoothly but I also re-measured the clearances:
Intake = 0015” (spec is ~.008”)
Exhaust = .008”

I could see a faint spark when turning the flywheel by hand. I then tested the magneto with a multimeter and was getting 2.9 kohms (low end of the acceptable limit).ould this be causing ignition problems?

Lastly, how freely should the flywheel spin? Is it normal when turning the flywheel for there to be more resistance during certain strokes? Should the flywheel spin a little on its own when I give it a turn?

Much appreciated.
Regards.

Click to expand...

so your intake valve has a clearance of 15 ten thousandths? unless my brain is failing me...
numbers don't mean much testing new ignition coils with the chip inside of them. usually either they spark or don't, or if they're bad, spark, but fail when hot.

Scrubcadet10 said:

so your intake valve has a clearance of 15 ten thousandths? unless my brain is failing me...
numbers don't mean much testing new ignition coils with the chip inside of them. usually either they spark or don't, or if they're bad, spark, but fail when hot.

Click to expand...

Yeah the clearance is way too low... so once I can get the engine started I plan to grind it down to spec and reinstall... I'm hoping the magneto is good...
Thanks again all for you help.. this forum is very beneficial

take out the plug and turn the engine over,
see if your plug is oily.
Yes, you need to do the exhaust valve correctly.

Fish said:

take out the plug and turn the engine over,
see if your plug is oily.
Yes, you need to do the exhaust valve correctly.

Click to expand...

Hi all,
So I managed to get the valves to spec and reassembled the engine. I left the carby off to test it. I did this by spraying some carb cleaner through the intake pipe.
After a few tries the engine completely seized ?
So I started by removing the spark plug and as soon as I removed it the cleaner squirted out. I continued until I stripped the whole engine and found a small metal lodged between the compression ring and the piston groove (see attached pics).
When rebuilding this engine I intentionally left out honing and replacement of rings because of cost and also because both seemed to be in good shape...

I’d like to hear your thoughts or ideas on how this could’ve happened and what to look out for moving forward?

Also, If I end up honing the cylinder, do I need to get a bigger piston?

Regards.

Time to cut your losses.
Carb cleaner can be a killer.

Try buffing out the damage on the cylinder wall, it is usually just pasted on aluminum, then all you would need is another piston.
If you have to go oversize, the prices go up pretty quick.

according to parts tree ONLY the .020" over piston is available, and ONLY the STANDARD ring set is available.
Might find some on Ebay.

Fish said:

Try buffing out the damage on the cylinder wall, it is usually just pasted on aluminum, then all you would need is another piston.
If you have to go oversize, the prices go up pretty quick.

Click to expand...

I’ll try buffing with some emery paper and scotch brite. If that doesn’t work I’ll hone it.
Then I plan to take out the piston and rings from a scrap engine and re-install (NO carby cleaner) I just want to get it working so I’m hoping this will get me over the line...?

Trying to diagnose the problem, I am thinking this could’ve happened because the cylinder wasn’t honed and therefore not well lubricated so the ring got caught in a gouge along the cylinder wall? What do you think?

I would say that the carb spray caused the lack of lubrication.

That damage was not from the carb cleaner. He said the engine had a tight spot as soon as he rotated the engine after working on the valves. That was the the damage to the piston and cylinder dragging. Aluminum cylinder, no buffing that out. Probably suffered the terminal scoring before he even started working on the valves. RIP rest in pieces.

Hammermechanicman said:

That damage was not from the carb cleaner. He said the engine had a tight spot as soon as he rotated the engine after working on the valves. That was the the damage to the piston and cylinder dragging. Aluminum cylinder, no buffing that out. Probably suffered the terminal scoring before he even started working on the valves. RIP rest in pieces.

Click to expand...

Fair enough, I’m probably better off just using the crank case on the scrap engine as well.

But what would’ve caused the scoring in the first place? There were no defects on the cylinder or piston after I cleaned them and I made sure all parts were well lubricated?

so did you rebuild this engine?

Scrubcadet10 said:

so did you rebuild this engine?

Click to expand...

Yeah, I took it off an old mower with the intention to rebuild and restore.

Something weird here. Maybe we can get out the Dick Tracy decoder ring and figure it out. Last post you say there was no damage to piston or cylinder when you cleaned and reassembled them. You also say in one of the early posts that as soon as you tried to turn the engine after working on the valves it bound and was difficult to turn. Looking at the pictures it looks like aluminum bits on the piston and a fair sized chunk stuck in the ring that gouged the piston and cylinder. The gouges are fresh. The other scratches on the piston look older and made while the engine was running. Doesn't matter now but where and when did the aluminum bits come from?

Hammermechanicman said:

Something weird here. Maybe we can get out the Dick Tracy decoder ring and figure it out. Last post you say there was no damage to piston or cylinder when you cleaned and reassembled them. You also say in one of the early posts that as soon as you tried to turn the engine after working on the valves it bound and was difficult to turn. Looking at the pictures it looks like aluminum bits on the piston and a fair sized chunk stuck in the ring that gouged the piston and cylinder. The gouges are fresh. The other scratches on the piston look older and made while the engine was running. Doesn't matter now but where and when did the aluminum bits come from?

Click to expand...

So I first took apart the engine, cleaned all the parts, lapped and adjusted valves (I ended up having to do this 3 times), replaced all gaskets and seals, lubricated the parts and assembled.
I didn’t hone the cylinder and I reused the rings. I also had to fill and drain the engine oil twice.
Regarding where the metal pieces came from, I’m not sure, It is possible some foreign objects found their way into the case while I was working on it (even through I was quite thorough in my cleaning), Or that the piston seized and scraped a chunk off the wall in my last attempt to start it with carb spray.
Regarding when the metal pieces were introduced, again I can only speculate, it could be they were in there from the first assembly when the engine was getting stuck, or last Saturday when I adjusted the valves and tried starting it with carb spray...?
I will inspect it again and see what I can find.
Regards.

Did you clean all of the valve lapping compound up good?

And have you checked the carb for missing screws