Cam timing

[I like karts]

Has anyone ever experimented with cam timing on a briggs 5hp? I know people do it on cars and I wonder what it would do on one of these. I think it would actually help if you are using the stock cam because of easy spin holds the intake valve open, and it would close sooner if advanced, thus raising compression. It would probably Idle like crap though (Oh well, I love bumpy idle). If anyone's ever done this, please tell me what results you got.

 

[2or3wheels]

i think it can be done, when you put the cam it you have to line it up with mark and if you advanced it a few teeth it would advance it i suppose, probly better off getting a bigger cam.

 

[jr dragster T]

You cannot do that. If you want a bumpy cam get a long duration and a higher lift.

 

[oscaryu1]

easy spin holds the intake valve open

It holds the exhaust valve open.

A few teeth? You'll be lucky to escape with only a sore hand...

There's no use advancing timing on a 5HP, unless you're running alky.

 

[Kenny_McCormic]

It holds the exhaust valve open.

A few teeth? You'll be lucky to escape with only a sore hand...

There's no use advancing timing on a 5HP, unless you're running alky.

Pretty sure its intake, stuff a rag in the intake port and crank it over, rag will blow out.

 

[jr dragster T]

uhh no. NO engine releases it's compresion threw the intake! And if a rag gets BLOWN out the intake then the engine has serious isues!!

 

[ed1380]

like bad timing

 

[Kenny_McCormic]

uhh no. NO engine releases it's compresion threw the intake! And if a rag gets BLOWN out the intake then the engine has serious isues!!

It was all disassembled and the rag was a tight fitting paper towel plug.

 

[oscaryu1]

Then you got problems. Honda GX200 Clone. When spinning it over by hand, exhaust rocker goes down very slightly before coming to the squish and boom.

On the Briggs 3.5HP's cam, the decompressing mechanism is on the exhaust lobe.

 

[Kenny_McCormic]

Runs great, the 8hp vert shaft on my beater mower vents the same way IIRC (been a while since I flooded it and had the air cleaner off).

 

[gocartkid]

An engine builder told me the intake valve holds open while the mixture is starting to compress (not very long mind you). Take the aircleaner off and squirt some ether or gas in the carb. Now pull the cord. You will see some vapor of whatever it was that you sprayed come out the carb if pulled slowly enough. I have a few Briggs 5hp engines that do this, and all are very healthy and run "like a race car".

 

[gocartkid]

Then you got problems. Honda GX200 Clone. When spinning it over by hand, exhaust rocker goes down very slightly before coming to the squish and boom.

On the Briggs 3.5HP's cam, the decompressing mechanism is on the exhaust lobe.

Yes, that is the newer ones. They stopped making the decompressing mechanism on the intake side due to backfires due to improper tunes, broken flywheel keys, etc. The exhaust is just the safest option. Ever gotten a backfire in the face from one with the mechanism on the intake side? I now understand why the switched....

 

[gocartkid]

Oh, and to answer the original question: DO NOT advance the cam a few teeth. You'll do more harm than good. Everyone here is right, just get a bigger/better cam.

 

[Kenny_McCormic]

Ever gotten a backfire in the face from one with the mechanism on the intake side? I now understand why the switched....

Nope, I keep my face away from the explosives factory.

 

[jr dragster T]

An engine builder told me the intake valve holds open while the mixture is starting to compress (not very long mind you). Take the aircleaner off and squirt some ether or gas in the carb. Now pull the cord. You will see some vapor of whatever it was that you sprayed come out the carb if pulled slowly enough. I have a few Briggs 5hp engines that do this, and all are very healthy and run "like a race car".

Yep he's right. If we start up our Junior dragster in the garage with no air filter you can see alcohol vapor pouring right out.

 

[gocartkid]

Haha, yea well sh!t happens!

 

[oscaryu1]

Yes, that is the newer ones. They stopped making the decompressing mechanism on the intake side due to backfires due to improper tunes, broken flywheel keys, etc. The exhaust is just the safest option. Ever gotten a backfire in the face from one with the mechanism on the intake side? I now understand why the switched....

Good to know! I was thinking along the lines of backfiring and such if it came outta the exhaust!

A few teeth... I'd like to see that happen! With an electric starter of course :rolleyes3:

 

[jr dragster T]

I'd like to see pull start lol jk.