Decomp - Use It or Lose It?

[bikemike]

Use it

 

[Philbert]

What is the difference between an oil seal leaking and a decomp leaking?

I'm not an expert on this, but will throw out my humble opinion for discussion . . .

- Leaking seals can lead to lean seizures, as they allow more air to mix with the fuel while still in the 'charge', inside the case, before it travels to combustion;

- Leaking decompression valve is more likely to lead to reduced compression during the power stroke, as that part of the cylinder is pressurized at that point.

Thoughts? Make sense? Blow it out my exhaust port?

Philbert

 

[jmssaws]

What is the difference between an oil seal leaking and a decomp leaking? Many more oil seals lead to scored cylinders than decomps. I'm with Ride Red. I use it for the convienience just as much as for wear and tear. And if it doesnt make a difference on my TM 066 because the button pops almost as soon as I start pulling pulling the cord, so be it. Then its for the psychological factor!!!!

Compression release is on the pressure side note the vacuum.

 

[Tor R]

As long I have health I trow them to the side and plug the hole, all my projects are plugged.
I have decomp on my 2253 but yet to use it.
If I got it correct Husky/JRed is working with a better coil now so they will ignite easier, if this is future decomp will not be needed at all.

 

[BGE541]

Plug them all...

 

[Terry Syd]

Maybe this thread is asking the wrong question. - OK, if you have a large displacement saw with a high compression, which de-comp would you use?

There is a big difference in de-comps from the size of the exhaust hole/s to the spring pre-load. They shut at different pressures, I expect a lot that pressure has to do with the flow rates through the de-comp (think displacement). So why not do, what you do to the rest of the engine - TUNE the freaking de-comp to the engine.

I had a Chinese de-comp I had to hold open with my finger as I pulled the cord. I would then drop the de-comp valve in the middle of the pull and the engine would start. I got tired of that drill and bought a de-comp with a stronger spring - problem solved.

 

[Terry Syd]

I just read through the rest of this thread. Some guys are worrying about LEAKING de-comps.

OK, I remember an article I wrote for a motorcycle magazine on IDENTIFYING THE PROBLEM. It started out with a guy I ran into that had broken off his clutch lever. I noticed that the mount was absolutely tight on the handle bar. I asked him why he didn't loosen the mount a bit so the mount could shift instead of the lever breaking = his reply - because the mount kept loosening up while he was riding.

I explained to him that that was a DIFFERENT PROBLEM, that was the problem of LOOSE BOLTS. You could fix that problem with lock nuts, lock washers, star washers, Loctite, tie wire - just set it up so that the bolt didn't work loose under vibration. - big DUH!

So why doesn't the de-comp seal. Maybe it needs some WD-40 flushed through it every now and then, along with twisting the valve back and forth to clean up the seat. Perhaps it was defective from the factory and need a bit of lapping with some light valve grinding compound.

If the de-comp is leaking, that's the problem that needs to be fixed.

I've read where some guys were saying a leaking de-comp could LEAN out the mixture. Come on guys, the intake is in the crankcase. The only leaking your are going to get from a de-comp will be COMPRESSION. It won't lean out the mixture at all.

 

[Deets066]

Good posts Terry!

I'm sure there are a few ways to fix leaky decomps. My way is just with a plug, I have no need for it so why take the time to fix it.

This is just my take on it, I know why people like them.

 

[RIDE-RED 350r]

^^^because we have pussy arms!! Lol! ^^^

 

[Deets066]

^^^because we have pussy arms!! Lol! ^^^

Do your arms look anything like Randy's legs?

 

[angelo c]

I just read through the rest of this thread. Some guys are worrying about LEAKING de-comps.

OK, I remember an article I wrote for a motorcycle magazine on IDENTIFYING THE PROBLEM. It started out with a guy I ran into that had broken off his clutch lever. I noticed that the mount was absolutely tight on the handle bar. I asked him why he didn't loosen the mount a bit so the mount could shift instead of the lever breaking = his reply - because the mount kept loosening up while he was riding.

I explained to him that that was a DIFFERENT PROBLEM, that was the problem of LOOSE BOLTS. You could fix that problem with lock nuts, lock washers, star washers, Loctite, tie wire - just set it up so that the bolt didn't work loose under vibration. - big DUH!

So why doesn't the de-comp seal. Maybe it needs some WD-40 flushed through it every now and then, along with twisting the valve back and forth to clean up the seat. Perhaps it was defective from the factory and need a bit of lapping with some light valve grinding compound.

If the de-comp is leaking, that's the problem that needs to be fixed.

I've read where some guys were saying a leaking de-comp could LEAN out the mixture. Come on guys, the intake is in the crankcase. The only leaking your are going to get from a de-comp will be COMPRESSION. It won't lean out the mixture at all.

I forget where and who said it but they "lap" the valve stem on dcomp buttons and had some success with lapping compound and a power drill. Chuck the tip in a hand drill and seat the valve tighter...
All the failed decomp I removed/replaced were gummed up with carbon from combustion byproducts. Had a few flat out bent to chit but they were oddballs from tree service gorillas. Those SOBs break anvils with toothpicks somehow.

 

[Jughead]

Only saw i have with a decomp is my 288.just haven't had time to plug it.reminds me..... @Definitive Dave i need some decomp plugs.did you get my last pm a few days ago?doesn't seem that my pm's are getting thru??????

 

[Definitive Dave]

I will add a couple to your box, sorry I missed yer message, I am a premium slacker

 

[Philbert]

Are decomp plugs different from a bolt at the hardware store?

Just curious.

Thanks.

Philbert

 

[Definitive Dave]

Yes!!!!

 

[RIDE-RED 350r]

Do your arms look anything like Randy's legs?

I've never done a side x side comparison... Hope I never have too! LOL!

 

[Philbert]

Yes!!!!

Can you elaborate a bit on the differences?

Thanks!

Philbert

 

[smokey7]

As far as I know you can use a bolt from the hardware store if you know the correct length to cut it too. Also you will need a copper washer to seal at the flat surface on the cylinder. I have heard it's not right and to use a plug. But I have been carefully doing it this way when in a jam.

So let me have it am I wrong

 

[Definitive Dave]

if you cut it to the right length and get a decent copper washer it is likely just fine but as cheap as they are......

 

[Philbert]

Copper is better than Permatex?

Philbert