advance OR retard timing ?

[java_scum]

Here's my setting to know ;
Suzuki RGR-150cc bored up to 153cc. I have set the dome volume to 9-9.5cc and 25mm exhaust height from the top. I use pertamax-plus fuel 96-octane pump-gas. Mikuni TMX 38mm carb with 260 main, 65 pilot, 5-clip richest and 1.5 turn out. and 15degree advance timing.

I have used it to run from 1/4 to 1/2 throttle with no problem,, BUT from 1/2 to WOT it seemed it has knock problem

It cause by timing ignition or the lower octane fuel I used ?? please give me advice

[flotek]

geez + 15 degrees is alot of advancment ...that is probably causing detonation kick it back to +3-5 or so and see if it helps ,i bet your going to get a big fat hole on top of your piston if yo udont change something soon

[gh500]

I'd put some good fuel in it first thats over 16:1 UCCR

[java_scum]

3 to 5 degree BTDC and higher octane fuel.. do you think avgas can handle it ??

I have installed suzuki RM125 ignition-kit that used internal rotor. when I tried to set the timing to 12deg with timing-light (retarded), the light became more rapidly than before (15deg) so I turn back to set 15deg because I worried it blow the engine (first time I used the timing-light ).
do you think it's normal if I set to retard and the timing-light become more rapidly ??

[gh500]

16:1 id look for some 110 octane to try first

did the rpms go up with less timing ?

[jj67]

What is your compression at? I would hazard to guess it's between 180 and 200 lbs depending on altitude (educated guess, based on displacement vs dome size), that will be the major factor on determing whether it is fuel or timing. On my LT250r, with 155lbs compression@3200' above sea level. I use a 50/50 mix of C-12 and 91 Octane pump gas, for a final octane of roughly 100 and I use Amsoil Interceptor mixed at 32:1. C-12 in my area goes for $25 a gallon, so it's awfully pricey. You probably need to run higher octane fuel. On 91 octane pump gas my LT knocks so badly at idle you would swear the bottom end rod bearing was toast, needless to say I didn't run it for very long! According to my owners manual, stock timing on the LT is 9* (maybe 6*, don't have manual here right now) at idle, and I believe 11* max advance, check what the stock specs should be and adjust accordingly if necessary. You may need to adjust both.

Do not run Avgas, it is designed for lower rpm's and high altitude, it really is not designed for bikes/quads, a good high octane race/pump fuel is much better. I say high octane pump fuel because I understand that Sunoco has 100-105 octane at the pumps? I live in Canada and we don't have Sunoco stations so that is third party info.

Hope this helps,

JJ

[nd4speed]

I can buy Sunoco 110 Turbo Blue at a station pump here in Michigan about a half mile from my house.

[flotek]

the only thing really worng with aviation fuel is its octa ne rating is just over 100 whic h is nt for everybody ....some bikes just plain need high octane like 110 to resist detonation ...otherwise its an excellent alternative.

[java_scum]

Originally Posted by gh500

16:1 id look for some 110 octane to try first

did the rpms go up with less timing ?

yeah,, higher octane need attention here.. here I can't buy like racing-fuel (there is no seller here) but someone sell avgas to me and sounds like alternative to my engine

I have compare the timing-degree between 15deg and retarded (lets say 12-8deg). at 15deg the rotation (full throttle) become more easily reach and sounds like detonation, BUT at 12-8deg the rotation (full throttle) slightly stopped like has rpm-limiter and sounds like detonation go away. what's wrong here ?

not yet check the piston for detonation axactly,, maybe tomorrow I will check for it

bore 60.25mm
stroke 54mm
exhaust height 25mm
dome 9-9.5cc
I haven't check the pressure in lbs...

[java_scum]

I checked crown piston and detonation .. but the centre and ground electrode seems ok (I guess there was not overheating).. next week I will charge the engine with avgas to try