# B&S 6.5HP OHV: Bent Intake Pushrod



## Colt Hero (Apr 23, 2007)

Briggs and Stratton, 6.5HP, OHV, model#121682 (I believe). End of last season discovered a bent intake pushrod. Finally got around to dismantling the engine this weekend. The intake (larger) valve appears to be stuck in the cylinder head - won't move freely like the exhaust valve does. Not sure what to do. I was going to apply force, but I thought I'd get a second opinion first. On the rocker-arm side, comparing the two valves, it looks like the cylinder head has a small circular silver "collar" through which the exhaust valve shaft moves freely, but with the intake valve it looks like this "collar" may have been pushed into the hole because it's flat or even recessed. Could this be the reason the intake valve's shaft is stuck? Also, I noticed that the valves didn't have the same hardware on the rocker arm side. The exhaust valve has a spring, retainer, and cap. The intake valve has these three pieces PLUS an extra circular "cupped" washer that sits between the face of the cylinder head and the spring. It seems like BOTH valves should have this piece since it seems to act as a "seat" for the spring, but the springs have never been removed, so this is the way it came from the factory. Also, I put this piece on the exhaust side to see how it fit and it didn't sit flush due to the "collar" I mentioned above - which led me to believe that the intake's recessed (or pushed in) "collar" might be OK. 

How should I free up the intake valve? The tappets appear to be working OK inside the engine when I turn it, so I'd like to just install the new pushrod and see if she'll start up again. Also, how do I find TDC on this thing? I think I need to do that, right?


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## oscaryu1 (Mar 25, 2007)

use a bit of force, and does the intake come out at all?


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## Colt Hero (Apr 23, 2007)

I ended up lightly tapping the intake valve out with a hammer and nail punch. After cleanup everything looks pretty pristine to me. I bought some valve lubricant and a sheet of cork to cut a new valve cover gasket. The head gasket is made of rigid material and looks to be reusable. I will try to put it all back together this coming weekend. Hoping for the best. At least it'll be very clean and full of oil for once. Not sure how the pushrods and valves will pan out. Not even completely sure how to time the engine. I think I need to get the piston to the TOP of the cylinder when both valves are closed (which I think I'll do by placing the pushrods into the tappets against my palm as I turn the flywheel). Then, what is it - when the piston is about 1/4" down from the top of the cylinder, the valve clearances between the caps and rocker arms needs to be verified? Do I really need to do this since I haven't altered the rocker arm nuts or their stud nuts against the face of the head? Shouldn't it all still be right? Still not sure after cleaning out the head that those "collars" around the holes that the pushrods go through are right. As I said before, the exhaust "collar" is raised up above the surface of the aluminum plate bolted to the face of the head, but the intake's "collar" is recessed below this plate into the hole. If you look from the backside of the head you can see this cylinder sleeve inside on the intake side, but no such "sleeve" on the exhaust side. Found a B&S repair book in a bookstore this past weekend that had color pictures inside. One picture appeared to show the head with the raised and recessed "collars" I mention, so that made me feel a bit better. Still looks weird to me...


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## 30yearTech (Sep 14, 2006)

You should check the valve clearances after reassembly, gasket compression can make a difference, as well as the push rod. It would be a good idea to replace the head gasket, but thats up to you. Make sure the valve guide is not loose in the head or you may have a repeat of the bent push rod in short order.

Good Luck....


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## Colt Hero (Apr 23, 2007)

The valve guide or the pushrod guide? The valve guides must be those "collars" I've been questioning. They look solid (but assymetric). The pushrod guides are the plastic/nylon inserts (I think) and those look OK too. Somehow, I'm in the state I'm in because the intake valve seized up causing the tappet to crush the pushrod against the rocker arm of the frozen valve. Maybe it was lack of oil? I think some oil had been getting by the valve cover before this all happened. 

By the way, anybody ever cut their own gasket from a sheet of cork? I've never done it and question if it's really doable, but I'm going to give it a try. I'm thinking I need a really sharp razor blade and then just make sewing-needle-like perforations along a line, not continuous cutting as this will probably end in disaster with two cuts so close together (1/4"?)


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## Rundell (Apr 30, 2007)

For the gasket, I have never made one out of cork but made one from thin cardboard. Fixed my oil leak on the bottom of the engine!


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## oscaryu1 (Mar 25, 2007)

just order a gasket, from a lawnmower shop or the internet.. or just buy gasket paper from somewhere like pep boys..


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## Colt Hero (Apr 23, 2007)

*Running For Governor?*

Well, the 6.5 B&S OHV engine (121682) is back together and running and it works! Cut the grass for about 45 minutes and the new pushrod didn't fail. One problem, however: The engine is running VERY STRONG - too strong - probably at RPM that is higher than it should be. Do I need to adjust some screw somewhere (I did not change anything to this point), will the engine seetle down on its own over repeated use, or do I have a problem with my throttle lever and associated linkage? I'm guessing it's the latter. 

[Note: I was very careful when I disassembled, writing everything down step by step. I don't think I lost any pieces, but I guess it's possible something may have been lost when the mower stopped working at the end of last season (and I didn't immediately know why at the time)]. 

The reason I think it's the latter (linkage problem) is the user's "Hare/Tortoise" throttle lever on the side of the engine is not doing anything. As I slide the throttle lever from "Hare" to "Tortoise" and back the engine doesn't change RPM. I've got the long, thin, aluminum 'bar' (called governor linkage?) hooked to the lever at the front of the engine and also back to the swivel bracket on top of the carbeurator at the other end, but there is only a wimpy (but pristine) spring hooked between the throttle linkage and a "curly-Q" loop in the governor 'bar' that appears to be the only means for the "Hare/Tortoise" throttle lever to actuate the lever at the front of the engine (which I think is what needs to happen)! It really seems like there should be a more direct/rigid connection (without a spring) doing this because while the "H/T" throttle lever DOES move the spring a little bit, it's nowhere near enough to move the lever at the front of the engine because the wimpy spring absorbs all the movement! Am I missing a piece here? 

One other thing: my notes said to connect the (carbeurator-side) hook at the end of the governor "bar" to the swivel bracket on the top of the carbeurator (which moves the butterfly inside the carbeurator chamber). Problem was there were TWO holes in this bracket and the 'bar' fits into both of them (didn't notice this originally): one more toward the edge of the bracket and one more toward the pivot point. The latter had a "collar" around it (sort of rivet-looking) that appeared chaffed around the edge, so I hooked the "bar" here. Regardless, though, I tried both holes before bolting the carbeurator to the engine because I wasn't impressed with the "action" on the lever toward the front and neither seemed to do much better than the other. It really seems like with the spring in there, you're never going to get the pull on the front lever (via the long rod) that you really need. That's why I think I might be missing a piece - like a 2nd (more rigid) spring, or even another 'bar' that links the user's throttle lever directly to the lever at the front of the engine (to change the RPM).

Any ideas?


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## Colt Hero (Apr 23, 2007)

Read through a pretty good B&S Repair book yesterday (beautiful glossy color pictures inside) to try to gain some insight on why my mower is running at such a high RPM after repairs. Apparently there are two things controlling the speed of MY motor (maybe slightly different for different motors): 

1.) The mechanical governor - which includes the long, thin, aluminum linkage "bar" and throttle linkage together with the carbeurator throttle lever, and ...

2.) Something inside the engine that I think they called "flyweights" that move based on centrifugal forces while the motor is turning.

The "flyweights" and mechanical governor are in a constant tug-of-war to control the engine RPM. When the mower is NOT under load (running on the driveway, for example), the engine wants to rev higher, but the centrifugal forces on the flyweights act to pull back on the throttle. When the mower IS under load (cutting grass), the engine turns more slowly with less centrifugal force which weakens the flyweights pull to close the throttle. But at the same time, when this happens, the spring of the mechanical governor acts to open the throttle to increase RPM. 

So my problem may be internal to the engine: the flyweights not pulling back on the throttle under no load (or ANY load, for that matter). 

Is it possible to determine this without completely dismantling the engine???

However, even if this IS the case, it still wouldn't explain why the user's throttle lever is not having any effect on engine RPM. Maybe I'm missing an extra piece of linkage, or - if not, I may have to retrofit one so I can at least get the high-end RPM down to an acceptable level (that won't destroy the engine prematurely).


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## 30yearTech (Sep 14, 2006)

check the throttle linkages and make sure the carburetor is hooked up properly. Yes you can check the governor operation without tearing down the engine, but first thing is to check linkages and make sure the throttle shaft in the carburetor is free and not stuck or sticking.


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## oscaryu1 (Mar 25, 2007)

Some engines just run faster than the regular speed. My briggs at max goes to 3800 RPM at full speed. get a tach or somehting to measure you RPMS


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## Colt Hero (Apr 23, 2007)

30yearTech:

As far as I can tell, everything is connected properly (as it was before I started). As far as the carbeurator, I'm not sure how it could be connected improperly. It just bolts to the side of the engine on top of the throttle bracket with the black plastic air cleaner assembly on top of it. I can tell you it's clean and the swivel bracket moves freely on top. And, as I think I've already mentioned, sfter hooking the long, thin "bar" into the top of this bracket, I was able to get decent "action" on the swivel bracket as I slid the user's throttle lever back and forth - but only with the carb. unbolted and physically further from the engine than it would normally be when bolted on. Once bolted to the engine, there just wasn't enough tension on the spring to get the swivel bracket on the carb to move when the user slid the throttle lever. One thing that was odd (?) about the carb. swivel bracket was that if could be "fixed" in position (don't remember if it was fully open or closed) by turning the bracket all the way to one end. In this position, the bracket fit perfectly around the contour of the carbeurator's cap, essentially locking it in this position. It may have even made a "snapping" noise! Is this by design? The butterfly is supposed to be adjustable, so I don't know why the swivel bracket could be "locked" into place like this. Looked to me like if the bracket ever turned all the way to this end, it could get stuck in this position! 

oscaryu1:

I'd have to buy a tachometer, and then how would it connect to the mower? Take off the blade and afix some free-running cable to the crankshaft underneath?


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## oscaryu1 (Mar 25, 2007)

the tachs ive seen connect to your spark plug... which maybe alittle hard if you hvae a plug boot


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## Colt Hero (Apr 23, 2007)

Is it possible my put-back-together mower isn't getting any oil? I ran it for 45 minutes to cut the grass right after I put it back together and it ran fine (except at a higher than normal RPM), but someone told me not to run it again until I disassembled the engine and verified that the flyweights were OK because there was some gear inside associated with these flyweights that was responsible for feeding oil to the engine. When I responded that I thought he was referring to the "dip tube?" on the end of the piston connecting rod, and since the engine was running it MUST'VE been getting oil, he said that would only be the case with a horizontal engine. With a vertical engine (which mine is), the piston is moving side to side and thus it is not dipping into any oil. 

This seems plausible to me, but who's right? Could I have cut my grass for 45 minutes without oil replenishment and not seized the motor up?


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## Colt Hero (Apr 23, 2007)

Took a chance and cut the grass again last night (45mins). Seemed to run OK, although still at a higher-then-normal RPM. 

Seems I'm in the clear now as far as the motor getting oil. If it wasn't getting any oil it would've seized up by now, right?

DID notice a (relatively dry) oil spot underneath the mower as I pulled it out to cut the grass, however. Never had this before, so there's a leak somewhere. I KNOW the gasket on the valve cover needs replacing, but I doubt this could've caused the spot on the floor. That oil would've most likely stayed on top of the deck. Maybe there's a leak straight down via the vertical shaft? Couldn't look at it last night because I starting cutting too late...


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## crazy_ate (Jun 27, 2007)

I have the same model B&S engine 6.5 HP Intek (121682-0122-E1-990330FA) and I am having a weird problem with the mower starting and then stopping and once it gets going the idle is rough (i.e., "hunting").

The problem just started out of the blue and becomes even more interesting because my dad has the same mower purchased about the same time several years ago and it just died (may have been a valve related problem, haven't disassembled the engine as of yet).

Anyway, back to my idle problem. Took apart the carb, cleaned everything (I think I know what I am doing seeing as I was a mechanic for several years), new plug gaped to 0.030", new air filter.

I took of the filter cover and filter to get a better look at the linkage while the mower is running and noticed that the "governor link" moves back and forth albeit it slightly causing the rough idle -- not too dramatic mind you, but certainly different than the very strong and steady idle I remember when things were running fine. When I put the front drive wheels in gear the idle surging gets even more pronounced and I feel that the engine is clearly not running its best.

While I had the air cleaner and cover off I over rode the governor link and manually idled the engine at both low and high RPM's -- steady as she goes. Then let go of the governor link and right back to up-down-up-down.

Seems that the problem is related to the governor link and that the source of the governor link movement is being cause at the end of the link where it is buried in the engine compartment -- which according to the above discussion may mean some sort of flywheel weights issue.

Any other thoughts before I tear into this thing? Thanks!


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## Colt Hero (Apr 23, 2007)

Well, the mower finally died (about two months before the end of the cutting season) last fall. On the last cut, it kept dying and I had to keep pulling the cord to restart it. Each time it restarted, it had less and less power. Never did finish cutting the grass. Ended up with oil draining onto the deck and a frayed pullcord that wouldn't retract. Seemed like everything failed at once. 

Questions:

1.) Right now I've removed the motor from the deck because I'm leaning toward buying a replacement (same or similar motor, if possible). I need an accurate measurement of the shaft length and diameter and need to remove the collar on the shaft that the blade bolts to. How do you get this thing off? I removed one of these things a LONG TIME ago, and I thought I remember extracting some tiny metal keys from the grooves on either side of the shaft. I can see a slim rectangular grooves on either side of the shaft, but neither has a metal key inserted inside. Does it screw off the shaft??? This is one of those collars with only a center bolt hole (which I never thought was very safe). Also, the PTO pulley needs to come off, but I THINK that's just held on with an allen bolt...

2.) Could I buy just a "short block" to save some money? What's missing on a short block typically?

3.) What do you think happened to my engine? It was running TOO STRONG after I replaced the push rod and I knew something wasn't quite right, but I was trying to get through the cutting season before opening it back up to investigate. Maybe the higher than normal revs wore the engine out?? It had the right amount of oil in it...


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## Restrorob (Dec 23, 2007)

Colt Hero said:


> How do you get this thing off?



Screw a longer bolt into the crank and use a gear puller if it won't slide off by tapping. There is also a square key slot along with the woodruff key slots.



> Could I buy just a "short block" to save some money?


If your head/valves and valve guides are still in good shape along with the carb then a short block could be a little cheaper.



> What's missing on a short block typically?


Everything external, A short block is nothing more that the block with all internal parts. 




> What do you think happened to my engine?



Lord only knows, A tear-down inspection would tell a story.


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