valve adjusting

[tng6664]

Hello everyone,, need help please. I have a craftsman with a 19.5 briggs & stratton twin i/c platinum turbo cool motor. The motor barely spins over,,,,when I take the plugs out it spins just fine. I've had several people tell me the valves need adjusting. Makes sense to me,,I have a little mechanical exp. with auto engines. The big problem i'm having is;;;; this twin head motor. under the intake are 2 covers that I thought would give me access to the rocker arms to adjust valves. I was wrong,, under the covers are just the valve springs. I see no rocker arms or anything else. Is there a way to adjust on these twin motors set up like this? Help,, I am lost. Thanx

 

[ILENGINE]

In a nut shell, the answer is no. You adjust the valves on that engine, by removing the heads, removing the valves, and grinding the valve stems shorter to adjust the valve gap. These types of engines usually don't have a problem with gaps too wide, They normally get narrower over time.

I find the common issue I see with this engine, is the starter gets weak over time, and will barely turn over the engine. Almost seems like the battery is going dead or something. The starter turns, but turns slower than required to start the engine.

 

[tng6664]

In a nut shell, the answer is no. You adjust the valves on that engine, by removing the heads, removing the valves, and grinding the valve stems shorter to adjust the valve gap. These types of engines usually don't have a problem with gaps too wide, They normally get narrower over time.

I find the common issue I see with this engine, is the starter gets weak over time, and will barely turn over the engine. Almost seems like the battery is going dead or something. The starter turns, but turns slower than required to start the engine.

I have 2 of these exact mowers,,,,I put the starter on my other mower and it turned that one fine. I've tried the same battery, solenoid . on the other. Everything works fine on my other mower,,,when I swap what I know to be good parts back, the motor will only barely turn with the plugs in. Not fast enough to start up. HELP

 

[natenkiki2004]

I've had issues getting my Briggs Twin II running (set it aside to work on other projects currently) but I contacted a guy that knows quite a bit about these engines and he sent me a writeup that he's made over the years with his hands-on knowledge. Here's what he said:

Difficulty starting B&S opposed twin engines, series 40, 42 and 46, is a fairly common complaint. The starters on these engines are pretty well taxed to the limit when everything is ideal so it doesn稚 take much to cause problems. Below is a list of some of the more common causes.

Check battery that it is good AND has good connections, cable not partially broken at terminal. On rare occasion a new battery may be bad or not completely charged. The ground cable connection to the frame is an often overlooked place. It should be bright and clean.

The top starter bushing, where the shaft exits the case, often wears oblong on these. When it gets bad enough, the armature will drag on the field magnets OR sometimes a field magnet will come loose or a small pc. may break off causing drag against the armature. Brushes can wear out but not really common. Starter gear may jam against flywheel ring gear. Also on very rare occasions, a small alternator magnet may come loose under the flywheel jamming the flywheel.

If nothing here and starter will not turn the engine over, try jumping directly to the starter from a known good battery. If engine turns now, use a small jumper between the positive battery terminal on the starter solenoid and the small activator terminal on the starter solenoid. If the engine turns now, problem is in safety switches OR ignition switch.

Battery and cables check out OK, engine tries but just can稚 turn over, besides starter problems listed above, excess carbon build up in the cylinder head is a common cause. IF engine can be started, use SeaFoam or similar product per instructions on the can. Otherwise, carbon can be removed by removing heads and scraping out. This will require new head gaskets.

Engines starts cold but not at running temperature, carb float needle may be letting some gas leak by causing flooding until gas evaporates off. Close gas line shut off valve 15 seconds before stopping engine, no shut off, clamp, pinch, rubber gas line. Electronic Ignition may be on verge of failing, check for spark.

These engines use an 摘asy Spin camshaft grind which holds the INTAKE valves open very late into the compression stroke. Excess Intake Valve clearance will keep this feature from doing its job. This usually happens right after someone has done a valve job and done it poorly. When valves are originally set properly they very rarely need adjusting on this engine.

Walt Conner
wconner5@frontier.com


From one person to whom I sent these suggestions:

I took all the electric connections loose and recrimpted them. I then took my dremel tool with a sandpaper wheel and cleaned all of the ends. I removed the paint from the chassis behind the solenoid. Even though the starter was new, the jam nut for the connection could be turned almost a half of a ?turn. After putting everything back together, It turns over real good. It pays to never assume if everything is correct even though everything except the wires were new. Thanks again for the good advice, especially about how the starter is doing all it can do even in a good situation.

Personally, on mine, I've re-done the wiring (sanding connections to frame, soldering instead of crimping, larger gauge wire), cleaned the starter out, bypassed the solenoid, bypassed all wiring and a few other things. Right now, I have the heads off and after cleaning I will check the valve gap (stick a feeler gauge in where you saw those springs) and then I'm going to get a brand new AGM battery as I suspect the one I was using was faulty or not charged fully. After that, if it doesn't work then it just might be scrap metal

 

[BAGGMAN's MOTOR SHOP]

In a nut shell, the answer is no. You adjust the valves on that engine, by removing the heads, removing the valves, and grinding the valve stems shorter to adjust the valve gap. These types of engines usually don't have a problem with gaps too wide, They normally get narrower over time.

I find the common issue I see with this engine, is the starter gets weak over time, and will barely turn over the engine. Almost seems like the battery is going dead or something. The starter turns, but turns slower than required to start the engine.

ILENGINE'S answer is the one i would go with . I never come across any L head that valves would cause that problem. My rule is "you can take an opposed twin starter, rebuild it and use it on a single cylinder (change the upper bracket of course) and it will work ok. Rebuilding it and using on opposed twin is hit and miss. repalce it with a new one." Valves adjustment is a common problem for OHV engines, turn a half a round and stop. There where some issue with early OHV having flat cam lobes and compression release not working.

 

[natenkiki2004]

I never come across any L head that valves would cause that problem.

To emphasize this, today I had some spare time and started dismantling my Briggs twin to check the valve lash. Mind you, I only checked one side so far but it was at .004" intake & .008" exhaust. Briggs specs .004" intake and .007" exhaust with springs installed. My engine was neglected by at least one owner. When I got it, the oil was below "low" and was as black as can be (it also had no air filter box cover, pre air filter and the choke was broken). Yet my valves (on one side) seem pretty good. I've seen OHV engines with far worse adjustments (much wider gap than spec) and still ran.

In my situation, I think I've narrowed it down to battery and/or starter as everything else looks great.


On a side note, I also have a rototiller with an old Briggs horizontal shaft L-head. It's from the 70's. It had issues backfiring through the carb. Checked it out and the intake valve wasn't closing all the way. The valve lash gap had shrunk down to nothing and is in constant contact with the pushrod, holding the valve at least partially open. I would think the opposite would happen, much larger gap with wear causing the valves to not open at all.

 

[BAGGMAN's MOTOR SHOP]

MAKE SURE YOU HAVE A GOOD GROUND AT END OF BATT CABLE. If its hidden down in the frame i will get a good set of jumper cables and run neg cable from the neg post on the batt to the enginie, just to make sure ground cable is not the problem. Are any of the gasket or seals leaking oil?

 

[tressler]

Sorry to hijack this post, but I am having similar problems. I though it was my starter, so I bought a new(used) one. Had the same problem, engine would only turn half way and stop. It's not my batter, not my cables... as I have jumpered around them.

I did discover something by accident, I tried to start it with only one spark plug installed (left side as viewed from seat), to my surprise, it fired right up! If I replace the right spark plug, it will not start...

Anyways, as my grass was getting really high, I cut the grass with only one cylinder firing, it was slow going, but I go tit done.

Where should I begin looking? Is this a valve problem? Is this a compression release problem?

It's a 19.5 hp twin I/C Briggs.

Thanks!

 

[tressler]

Still having this problem. I have been starting the tractor with only one spark plug installed and reinstalling the second after starting... getting old!
Is it just a bad starter? Could I have bought a bad (used) one?

Please, any advice would be great! Thank you!

 

[natenkiki2004]

Still having this problem. I have been starting the tractor with only one spark plug installed and reinstalling the second after starting... getting old!
Is it just a bad starter? Could I have bought a bad (used) one?

Please, any advice would be great! Thank you!

I would say bad starter still. My Briggs 18HP Opposed Twin did the same thing. It would crank slowly, and rarely start, but would crank like normal with 1 plug removed. Take your starter off, take it apart and look inside, you should see heat damage or scoring or something. There was plenty in mine. Bought a new starter on eBay and it's worked perfect. The starter I got a year ago was $33.90. I looked up my part number just to give you an example:
New Starter Briggs 399928 495100 498148 14 16 18 HP | eBay

It might be the same for yours too. So cheap though, you'll probably kick yourself for getting a used one Sure, they're not OEM, they're probably cheaply made in China. But I've been using mine for over a year and it's still going strong. Just don't abuse them, let them cool if you have to crank several times. They'll last.