billyt Posted April 7, 2010 Report Share Posted April 7, 2010 Jay This is right from VP Fuels web site. Not one mention about extra power purely that race gas affords one the abilty to fine tune the engine heads, exhuast, carb etc without pre-detonation due to the charactistics of the fuel. It also affords a more consistant source of fuel affording leaner jetting etc. That is why you may see a slight cleaner (adding race fuel only) running of the bike due to fuel consistance and leaner jetting but more power hell no!. What does octane really measure and how important is it? One of the most frequently asked technical questions we get at VP involves the difference between Motor, Research and R+M/2 Octane Numbers. The next most frequently asked question is why some fuel companies represent their fuels with Motor Octane Numbers, while other companies use Research or R+M/2 Octane Numbers. Realize first that octane is a measurement of a fuel Quote Link to comment Share on other sites More sharing options...
shercojay Posted April 7, 2010 Report Share Posted April 7, 2010 Ok this would depend on a few things, condition of the engine, air temperature as you must be aware that this makes a big different (being a mechanical engineer) and your definition of noticeable increase please Back to you der Freund( sorry no good at French) Quote Link to comment Share on other sites More sharing options...
telecat Posted April 7, 2010 Report Share Posted April 7, 2010 (edited) Everybody forgets that if you read the manual for all modern Trials Bikes the Minimum RON recommended for any Bike is 98RON. Hence if you are using standard Unleaded (95RON), you are losing out!! This is because the engine is set to run with this octane or better. As a rule most European car Engines are set at 95 Octane. However Volkswagen FSI and Japanese units run "Knock Sensors" which ajdjust the ignition for the higher rated RON fuels. As a Guide My 2 litre Lancer Estate does about 270 miles on a tank of 95 RON. On 99RON it does another 20-30 miles. Engine response is also better. Because the Fuel "burns" at a higher Temp it also burns off carbon in the cylinder. Edited April 7, 2010 by Telecat Quote Link to comment Share on other sites More sharing options...
billyt Posted April 7, 2010 Report Share Posted April 7, 2010 Jay......... This is getting nuts. You must be a female as you will not admit that you are WRONG! LOL.... Lets do this.............. yzeefoureight go mix up some high octane race gas, put in the bike. do nothing else to the bike. And if you are still alive after all of that power increase let us know how marvelous the power increase was! LOl..... Over to you amigo! Das es das liebien. BillyT Quote Link to comment Share on other sites More sharing options...
paulmac Posted April 7, 2010 Report Share Posted April 7, 2010 I'd be listening to Billy T myself - the guy knows about 'stuff' How's it hanging Billy? Paul Mac Quote Link to comment Share on other sites More sharing options...
shercojay Posted April 7, 2010 Report Share Posted April 7, 2010 Pmsl, no i aint a female,but to be fair i have enjoy this thread As for the higher octane fuel that maybe a good thing to try but i never said anything about race fuel!!!!! Lol and as for your German Billy Lol love it liebe dich auch Quote Link to comment Share on other sites More sharing options...
billyt Posted April 7, 2010 Report Share Posted April 7, 2010 Hey Paul It is not hanging anymore. I spilt some race fuel on it and it is driving me mad with power. It wants to go out and clean something. LOL How are things with you? So Jay. Lets try and help this guy as tag team to get more bottom end on his 125 si si senior! Okay? Please, no more silly magical horse power increase suggestion from puerly adding fuel. DEAL? Danka mein her. Quote Link to comment Share on other sites More sharing options...
shercojay Posted April 7, 2010 Report Share Posted April 7, 2010 (edited) I accept your proposal to agree to differ lol port and polish ??? or can you port from around then range? Edited April 7, 2010 by ShercoJay Quote Link to comment Share on other sites More sharing options...
no1 Posted April 7, 2010 Report Share Posted April 7, 2010 Any way as the ACU hand book says that fuel aditives are forbiden SO STOP USEING IT. And i no how to tune a 125 gasgas with loads of bottom end, mid range and top end that rev that hard it will make your ears bleed. But if i told you how to do it i would have to shoot you so sorry. Quote Link to comment Share on other sites More sharing options...
billyt Posted April 8, 2010 Report Share Posted April 8, 2010 (edited) yzeefoureight Firstly, I am not familiar with Gas Gas engines. BUT these principles work for all trials bikes. Okay Jay I will start. You pitch in at any time, or in fact anyone pitch in. If I wanted to increase a 125 cc trials bike for more bottom end, depending on the riders level of riding here is what I would do. An advanced rider: On a 125cc trials bike the bike is more than likely ridden with high RPM's most of the time. The bike in stock form is pretty close for high RPM riding. Leave the stock 26mm carb alone. I will explain why in the following changes to a 125cc if I was a average club rider. Change the head for a higher compression. Race fuel/ higher octane will be necessary now due to increased compression. Change timing. Open up the exhaust port to let the bike breath better. If I was average club rider and was NOT the greatest at revving the **** out of the bike to get up objects, hills rocks etc Here is what I would do to get more bottom end and snap with some torque. Change out the carb for a smaller one. Trials bikes usually come with a 26mm I would go with a 24mm. Why? The movement of the piston piston creates the vacuum on the carb. It will be the same level of vacuum regardless of what carb is on the bike. The smaller carb performs better on a smaller displacement bike for the following reasons. If the vacumm is the same regardless of carb size then a larger orifice carb such as a 28 mm will see higher air flow BUT lower velocity. This lower velocity (due to a larger throat on a 28 mm carb) will not aerate/atomize fuel at the venture as efficient as a 24 mm carb with a lower flow but higher velocity. The step from a 26 mm to 28 mm will gain flow but there was enough flow already with the 26 mm what we are looking for is mixing velocity at the needles/jets venture. A 24 mm carb has enough flow for an average club rider. In fact I always when possible switch out a the 26 mm for a 24 mm carb. This is carb basics. For the same amount of vacuum (air & fuel) to go through go though a smaller opening it has to speed up (velocity) making a better venture effect. The lower velocity from a 28 mm carb will feel funky at low rpm's and give the impression that one has lost bottom end due to running poorly/boggy lost snap due to funky fuel mixture. Granted the bigger carb will run better at higher RPM, and if you are a top flight rider on a 125cc you may want that? But I disgress, this segment is about an average club rider on a 125cc. I would also take off the jug/cylinder and either machine the base of the cylinder to lower the ports. Or if the jug has two gaskets remove one. Putting a thiner gasket is the cheapest and non destructive way of doing this. BUT not all manufacturers offer thinner base gaskets. If you do machine some of the base and you do not like the results or are now a top flight rider that needs to rev to the heavens then you can always put an extra base gasket back under the jug to take you back to where you started from. Lowering the ports by this method will also increase compresion and give some mid range power also. Obviously if money was no object then buy a spare jug and have the transfer ports lowered in the jug itself leaving the exhaust and intake ports alone. And for Jay. Wenn ich mich erh Edited April 8, 2010 by BillyT Quote Link to comment Share on other sites More sharing options...
shercojay Posted April 8, 2010 Report Share Posted April 8, 2010 I would have to agree with Billy on this, The only things to consider are- Money The ability to mod the engine yourself The impact and new stress levels on the engine You can port and polish your exhaust port yourself but that depends how confident you are in engine mods, Likewise for changing the head. I think the best option for you would be to change the carb However do you no someone who can set this up for you? Quote Link to comment Share on other sites More sharing options...
paulmac Posted April 8, 2010 Report Share Posted April 8, 2010 Hey PaulIt is not hanging anymore. I spilt some race fuel on it and it is driving me mad with power. It wants to go out and clean something. LOL How are things with you? So Jay. Lets try and help this guy as tag team to get more bottom end on his 125 si si senior! Okay? Please, no more silly magical horse power increase suggestion from puerly adding fuel. DEAL? Danka mein her. Hi Billy All good down here Must admit though we don Quote Link to comment Share on other sites More sharing options...
yzeefoureight Posted April 8, 2010 Author Report Share Posted April 8, 2010 Hi everyone, thanks for all the replys. Really useful. My dad can set it all up for me its just that we didn't know what would be the most beneficial and easiest way of gaining more bottom end power. There are loads of ideas on the topic but which do you think is the best? My bike has 2 base gaskets on it and my dad thought of taking one off as BillyT said but we asked at our local biike shop and said that it had been set up in the factory for the squish band, so I don't know now. What should I do? Thanks Sam Quote Link to comment Share on other sites More sharing options...
telecat Posted April 8, 2010 Report Share Posted April 8, 2010 Additives are allowed providing you do not exceed 102RON. This is because you can actually get this fuel commercially. I know one or two people used to buy Aviation fuel of this octane. Quote Link to comment Share on other sites More sharing options...
billyt Posted April 8, 2010 Report Share Posted April 8, 2010 (edited) Sam It has two base gaskets for a reason! That reason is taking one out to tune the engine. Of course it changes the squish BUT so does swapping for a modified higher compression cylinder head and people do that! If it were me! I would do the following in the order as I write. Take the cylinder/jug off Remove ONE BASE gasket Put the jug back on! THIS NEXT STEP VERY IMPORTANT! When putting the cylinder head back on and after torquing down cylinder head and jug/cylinder REMOVE SPARK PLUG AND TURN/PUSH START LEVER SLOWLY. This will verify that the piston is not hitting the lowered ( lower due to removing a base gasket) cylinder head! If it does NOT hit then proceed with re-assembly and then start bike as usual. You may have to increase the octane of the petrol If this first step works let us know and we can walk you through the next steps. Good luck! BillyT Edited April 8, 2010 by BillyT Quote Link to comment Share on other sites More sharing options...
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