Octane Booster safer than Aviation gasoline?

My Yamaha dealer has warned me about mixing aviation gas to increase octane level. It's a 'dry' fuel that reportedly causes burnt valves and pistons. It also contains a bit of lead which is not recomended in Yamaha's service manual, which mentions it can cause serious damage to valves and rings... I'll use Klotz octane booster instead as it's supposed to be the best one. It raises octane 2-1/2 numbers per ounce, up to 10 numbers. So I'll try 1.5 ounce per gallon with 91 octane fuel =94.75 for about $0.25+ per gallon.

octane booster can be evil stuff. a friend of mine in a sidecar once had his visor melt as he followed another outfit.

stick to avgas IF you can get it.


I used to race So. Cal. desert racing on a wide ratio 6 speed yz 250 2 stroke and forgot my 108 octane Trick Racing leaded gas. So I tried Moroso 110 octane booster added to unleaded super gasoline and about 35 miles into the race I burned a hole about the size of a .50 cent piece through the top of my piston at about 90 MPH. So I have little confidence in octane booster, however on my 426 I run 1/3 V.P. Fuels Ultimate 4 that is designed for 4 strokes and I have had no problem with it having a little lead in it. Also I used to drag race cars and have seen guys run aviation gas that can very in octane rating alot so I don't think it would be a good idea.

Stay away from Octane Booster! It is bad for the bike! :)

Aviation gas is not as dense as pump gas. It requires richer jetting and is not as efficient. It was formulated for high altitute low-reving engines and does contain lead.

Klotz claims to use a tetraethyl lead substitute. They won't tell me what's in it (probably an alcohol derivative), and it does darken plastic gas tanks. Most use MMT which will cause long term engine damage.

Here's some good info on all octane boosters and av gas: OCTANE

Check out this interesting info on toluene as an effective, safe and cheap octane booster: toluene

I've considered adding a cylinder base gasket to lower compression...not an easy task.

If disconnecting the TPS doesn't help, I could slot the ignition's pickup coil to retard ignition timing :).

It pings between about 4000 and 7000 RPM, at any load/throttle opening on 91 octane gas (best local pump gas).

Have you raised your compression? If not it should run fine on 91 octane pump gas.

Have you checked the ignition timing? It could be off. Also check for air leaks in the intake and exhaust, spark plug heat range or carbon build-up in the combustion chamber.

The engine is stock and compression hasn't been changed...no leaks and well jetted. It runs flawlessly except for the pinging.

Can the ignition timing be adjusted without removing the flywheel and slotting the pickup coil's mount? Today's '91' octane gas doesn't seem to live up to its claim. If I check the head for carbon or sharp edges, do I need to replace the $50 head gasket?

First thing I would try if you are absolutely sure there are no air leaks is a cooler plug. Its the easiest. Then check the timing. I have never changed mine so I'm not sure of the procedure, but you are probably right. The last resort would be to take the top end off and yes I would replace all the gaskets and o-rings. Its not worth risking a leak and doing the entire job over again.

Another thing I just remembered. I attended a seminar at Cycle Improvements over the winter. They recommend to always check the resistance of the spark plug cap and lead. They say they find a lot of bad ones - although it is a KTM dealer :)

If I check the head for carbon or sharp edges, do I need to replace the $50 head gasket?

Just my two cents here. I learned a long time ago, Do it right and do it once. Nothing worse than having to do a whole project again just because you took a short cut. Good luck.


Yeah of course...I really doubt there's any carbon buildup to be concerned with yet though. It's well jetted, valve lash is still spot on and I never fouled a plug. Everything is fine and it does run flawlwssly except for the pinging at the beginning of the power band. It was pinging only slightly on 92, now they've downgraded to 91 when it got worse...

I will start by trying backing off the TPS to reduce ignition timing advance when I take it out for 1st time this season on the weekend...

It's common misconception that octane boosters raise fuel octance as you suggest.

"It raises octane 2-1/2 numbers per ounce, up to 10 numbers. So I'll try 1.5 ounce per gallon with 91 octane fuel =94.75 for about $0.25+ per gallon."

But actually, it would only be 91.25. 10 numbers would make 91 octane into 92. So you see it's hardly worth the price of the stuff.

If you need higher than premium pump gas, go with race gas.

Actually, you are refering to "points". 10 points = 1 octane number. Klotz is probably exagerating, they won't even give me their magic recipe that darkens plastics. All octane boosters should be avoided, and some race fuel$ contain a dye that can gum up your carb and intake.

At any rate, retarding my ignition timing was enough to avoid the need for more octane.

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