Race Gas

[djr_austin]

I'm back with more newbie questions from the Brit on a new 4RT in Austin Texas :-)

On the promise of a cleaner burning engine, I moved from ethanol "enriched" gas in the 91-93 range, to VP 110 race gas.  Outside of the price, I like the stuff bar one thing.  I'm seeing some odd engine behavior in the following scenario.  When opened up on the loop trail out to one our our sections, when I'm  in a high gear with gas on, its feels like the engine in faltering and might even stall a little.  As I gas off it seems to idle down too fast - it recovers cos its a Monty :-) but does this imply something is wrong?  Shoud I have changed something with the gas? Should I not bother with the race gas thing and live with the fear of the "dirty engine later in life"?  

Thanks in advance for the help of this awesome forum.

[copemech]

Do you understand the fact that higher octane fuel is more difficult to ignite and totally useless in a motor not designed for its use. You will wind up with more deposits than if you had just put regular pump gas!

Use a fuel of the proper rating from a quality supplier that uses a good additive package for cleaning such as Shell or Chevron. Or I suppose you could just mix up a splash of Techron additive in the fuel cheaper fuels on occasion.

[bbk]

ive ran race fuel in my 4rt for for 11 years i have mixed it a few time with non ethanol fuel with no problems i do for the smell . And where can you find 95 octane pump gas unless your over seas your not going to at shell exxon or mobil .Here in Taiwan though octane is 91-95-98 pump gas no ethanol . any chance you reach the the rev limit ? my bike still like to drink the good stuff dont think its the fuel. 

 

[copemech]

Keenan, keep your RON and your R+M/2 methods straight!

[jonnyc21]

I found that my Montesa seems to do best on premium non-ethanol pump gas.  I do end up having to go out of my way a bit for it but with how well it runs it's worth it to me.  I found it works better than race Gas.

my 2 cents worth.  Hope that helps.

[slicktop]

1 part 110 leaded Race to 4 parts 100LL Avgas is my perferred blend.

Does Montesa require Unleaded?

[b40rt]

Having read through the comments above, how do 4rt's survive 6 days of thrashing at the ssdt, on standard pump fuel ?

[slicktop]

31 minutes ago, b40rt said:

Having read through the comments above, how do 4rt's survive 6 days of thrashing at the ssdt, on standard pump fuel ?

They may survive, but they haven't won.

[feetupfun]

This is a fairly eye-opening and entertaining thread

To answer the original query you should stick with the fuel that Honda recommend because "race gas" burns too slowly for a standard 4RT. The problems with burning too slowly are that it causes high exhaust gas temperature and the motor produces less power

[pschrauber]

 

The gas will not burn slower or even faster if you have more octan it will just ignites later.., with higher octane fuel you will have less chance of detonations'.

As more compress ratio the engine  has as higher has to be the octane number.

If you use 100 octane but you could too use 95 octane nothing will happen the bike will run as usual. As a benefit you will never have any detonations. As more you cone near by the recommended octane rate as a minimum as more is the chance getting detonations under load.

gasoline with lower octane will have the tendency to be ignored prior to the spark plug, will cause heavy detonation and can damage the engine quite easy.

Mostly race gas or gas with high octane is of very good quality and has less indegrents that are just mixed to the regular pump gas by law or economic benefit as bio alcohol certain stabilizer and so one, thus race gas is often a bit better in power output.

 

In my personal experience I like Aspen gas very much invented for forest machinery and based on Alcylate instead on oil.

It burns without soot and without smell can be stored for years comes with 95, 98 or 101 octane but it is expensive.

For a clean exhaust and engine, your health and the environment a real good fuel.

[b40rt]

4 hours ago, slicktop said:

They may survive, but they haven't won.

Apparently Toni Bou won't ride the ssdt because the fuel supplied is of the wrong octane rating .....

[fxstbi]

djr_austin, I live just east of Austin and I remember talking with you at last months trials in city park. I have a Beta 4t and a Montesa and I run both on avgas. They run great and I don't have any complaints running it. I do know the you can get 93 with no ethanol in Austin, a friend of mine runs it in his 300 RT and gets it somewhere in Austin. Avgas is available at most any small airport, I get mine in Smithville for 3.95 a gallon. 

[2stroke4stroke]

I have run my 4RT on both normal unleaded and super unleaded - can't tell the difference in performance and no signs of bad running - presumably the ECU sorts it out.  The Rev 3 definitely appreciated the super.

[trapezeartist]

I recall when 5 star was being phased out. I went to a lot of trouble for a while to go to a place that still sold it, then finally had to fall back on 4 star. It made no difference when I changed. I have always run my competition engines on the best pump fuel available, choosing the best just as a small safeguard that only costs a few pence anyway. Money spent on exotic fuels will always be better spent on more frequent new tyres (unless you already put on new for every event).

[bbk]

I was told on Avation fuel they mix something for  high altitude to keep fuel from gelling or something like that i used in my sweet bike at the time was told i shouldn't .VP fuel staion carry 101 octane at the pump. Alot of motorcycle dealers carry race fuel in there shops too. 

 But getting back to your problem doesnt sound like its the type of fuel. What year is the bike? whats the plug look like? how about the tail pipe clean or sooty?

 I did have an after market muffler on mine that the packing came loose and caused the bike to do as your describing come to think of it. 

 

Edited March 26, 2017 by bbk