Any Auto-electric Guys Out There?

[Somtham]

Sometime last year the mower started acting up and was difficult to start in the mornings. The starter would turn the flywheel but once it hit TDC on the compression stroke it would no longer crank. At that time I could start it using jumper cables from the truck. That eventually would not work so I recently took it to a mechanic shop in town.

The diagnosis from them was a bad starter so they sent it off to Bangkok to have rewound. After 2 weeks of waiting when I picked the mower up from the shop the guy said I had to wind the flywheel past TDC before starting. Uhgg. He started the mower up by doing this. OK, so I take the mower home and first try nothing but smoke and the smell of wires frying from the starter.

Back to the shop. The engine is a 18.5 Hp Briggs-Stratton from the US. The guy looks at it and yep the starters fried so he asks me if he can put a car starter on it and I said go ahead but I don't want to have to hand crank the flywheel everytime I need to start the mower. No pwoblem.

I go back 2 days later and the guy tells me no car starters will fit but his dad found an old Briggs starter in the back room so he put it on. Now, to start the mower I have to first crank the flywhell just past the compression stroke, remove the air filter and cover the carb with my hand and then turn the key. The starter cranks fine and the engine starts if I remove my hand form the carb at the right time. One other thing is that when I got the mower back this time the engines runs much much louder than it ever has.

So, does anybody have a clue what's really wrong with this thing and why it runs so loud?

Thanks for any advice offered.

rgds

[timi2546]

......

hi there.

have u checked all hoses

which are connected to carburetor....

seems it gets air too much,

if there's not black smoke

(too much gasoline then).

sometimes little things make

those little engines so mystical.

maybe i am totally wrong..

[denboy]

Perhaps your starter motor was weak in the coils or past it's best.

However you have a new starter motor so you need to look futher.

I am not familar with that particulat engine but I would suspect you have a ignition timing problem, I might even go further and suggest valve timing as I have no idea of the camshaft drive method. Did the mechanic check that side of it out?.

You did mention that it was running rough previously so there is more to it than a dodgy starter motor.

try a different mechanic or insist the same one check the basic timing by the book.

Good luck.

[Somtham]

Perhaps your starter motor was weak in the coils or past it's best.

However you have a new starter motor so you need to look futher.

I am not familar with that particulat engine but I would suspect you have a ignition timing problem, I might even go further and suggest valve timing as I have no idea of the camshaft drive method. Did the mechanic check that side of it out?.

You did mention that it was running rough previously so there is more to it than a dodgy starter motor.

try a different mechanic or insist the same one check the basic timing by the book.

Good luck.

Denboy - You may be right about the timing as when I started it up yesterday there was constant backfiring through the carb. That may also explain why the thing is running so darn loud. After I picked the mower up from the mechanic the first time he was very proud to tell me how they disassembled the entire engine. I asked how he set the timing and he told me there was a mark on the crank to align. I downloaded a parts diagram and it actually shows a timing gear between the crank and cam. Did he really line everything up? Guess I'll have to take it apart to find out for sure. By the way, the ignition spark is from a magneto with the magnet in the flywheel.

Timi - There are 2 hoses to the carb. One is the fuel line and the other is a vacuum line coming from the crankcase. No noticeable effect when disconnecting and plugging one end of the vacuum line.

Thanks for your suggestions.

[denboy]

Is the engine a twin cylinder or ?.

If a twin he may have lined up the marks 180 degrees out, engine will still run but like a bag of hammers. I don't know what purpose the hose from the crankcase to the carb do's other than a breather. Normally you have a hose to the manifold to advance retart ignition on earlier engines. I cannot envisage how it effects a magneto ignition.

Let us know how you solve the problem.

Cheers

[Somtham]

Is the engine a twin cylinder or ?.

If a twin he may have lined up the marks 180 degrees out, engine will still run but like a bag of hammers. I don't know what purpose the hose from the crankcase to the carb do's other than a breather. Normally you have a hose to the manifold to advance retart ignition on earlier engines. I cannot envisage how it effects a magneto ignition.

Let us know how you solve the problem.

Cheers

Ok, so grabbed a cup of coffee and decided to dig in this morning. Pulled the plug and removed the valve cover to see what was going on with the timing. OMFG. Valve clearance on the intake was about 0.075" and on the exhaust well over 0.125". Reset the intake to 0.006" and the exhaust to 0.008". Don't have a repair manual so am not sure if those are right. Put the valve cover back on and spark plug in. Turned the key and it started right up. No backfiring, back to normal dB level, no covering the carb intake, and no "winding up" the flywheel.

Now, are these "mechanics" that stupid? Or was this a plot to destroy the engine so they could rebuild it at a later date. Unreal.

Denboy - thanks for your replies and suggestions. The engine is a single cylinder and I guess the vacuum off the crankcase is an emmission thing to burn off crankcase vapors. The mower was purchased in California and they have very strict emmission standards.

Thanks again.

rgds

[denboy]

Pleased to hear that you found the problem, the valve clearences sound about correct. Depends on the model engine I suppose, the exhaust perhaps should be nearer 010' to allow heat expansion.

As for Thai mechanics being stupid, I think it is the lack of basic knowledge of how the parts relate to each other. If I go to the garage for any repair I stand over them and I am not shy in telling them when the do stupid things like ie ' tightening wheel nuts with a 4ft long steel pipe on the wheel wrench'.

I prefer to do my own repairs but age makes it a bit of a drudge.

Happy motoring around your lawn.

Cheers