YX150 engine

[headsmess]

if your maaaaates 125 is capable of going better than a 150, why think that bigger is better? 180? why bother?

maybe get his 125, that would be my plan of attack.... then work that....

even my stock 140 pulls over 110km and thats 17/36 on 10 inch rims... and a badly jetted carbie cus i be too lazy to tune it... and beats most things at the lights still

 

[Atomik rider 4 lyf]

Maybe your mate has gearing like mine 16/43 so then he would hav longer gears but less acceleration and thats y he cant get the front end up unless he pops the cluch cause thats wat i have to do and i have 16/43 gearing so if u wanna keep up wid him you would hav to loose the acceleration to gain bigger gears.
hope this helps

 

[themountain]

Alright so after some research and talking to my buddy at a performance shop, i think what i need to do to make me happy is

Buy a big bore kit like a 180cc

...to give a friend with a 125cc some heat...??...whats wrong with you boys??

I am with headmess...gear your bike right and tune it in and this thing will fly

 

[daimojay]

that link to my motor is wrong

My motor was still only a 155 in that clip.... gives u an idea of what a TBv2 ported, with a good cam, tuned decent carby (was only using the MOLKT) with a good clutch and gearing, rev limiter etc can give u great top end, with the power to get there..... fast


As for the 4valve heads.... im stick sceptical they can get the flow for the big bores.... and no ones trying it so i guess we will just have to see

 

[DvDRip]

I was referring to this one posted somewhere in that thread
YouTube - Yx187 helmet cam I love this video

 

[bse150cc]

Alright so i learnt something cool about the bike today!!! it was rich in the top end that was my issue... i had a 115 in it, and it would feel like im hitting a rev limiter, when really it was jsut ot much fuel, i put in a 112.5 and now the thing pulls like a mofo up top, im gonna try and drop the needle down a clip and see what that does!

 

[daimojay]

told you to tune it properly

even a 115/112.5 is pretty big for a 150 stock :/

There is alot more to reading plugs then just looking at the end of them ^.^

 

[bse150cc]

still has a little miss in the bottom end, something in the pilot circuit.. it had a 25 pilot, put in a 27.5 then tried a 30.

None of them really changed much except the 30 made it act weird like it was starving for fuel so im gonna play with it some more!!

 

[Cactus Jack]

Well that tells you that you're going in the wrong direction with the pilot jet ... I knew the main jet was too rich ... You should keep going down in size until the motor stops pulling hard up top ... then go back up one size ... Cases cracking after fitting a high compression piston 'aint weird ... What IS weird is how people think you can jack the compression up without having to back the ignition timing advance off ... some people actually think you need to advance it ... LOL ...

IQ test ... how do you make a bomb ?

1) by spreading gun powder loosely in a bucket ...

2) by packing it as tight as you can into a sealed thick walled steel container ...

Now apply your answer to an explosive gas mixture trapped and compressed in an engines cylinder ...

Do you light the "bomb" ...

1) So that it will explode before the piston has reached true TDC causing the engine to "fight" against itself ... ie attempting to force the piston and crank backwards ... effectively lowering the power output and overloading parts to the point where they can easily be damaged ?

OR :

2) Time it accurately so that the maximum force of the explosion happens just after TDC where the full cylinder pressure will go into driving the piston and crank as hard and as fast as is possible in the proper direction ... thus making the bike go as hard and as fast as is possible ? ...

When you raise the compression you'd better have a fully adjustable ignition advance / retard curve then use the least amount of advance to get the best results as verified by a dyno OR by stop watch timed standing start runs over a measured distance ... Just going by "feel" or "imaginary dyno" is the surest way to blow an engine up ...

Any kickback (aka detonation) whatsoever is damaging to an engine and repeated kickbacks can start cracks off that are invisible to the human eye ... That's the reason why race engines are X-rayed and sonically tested when they are going to be rebuilt ...

 

[themountain]

^^^^^^...there you have it...cactus once again solid info!!

 

[daimojay]

cactus, you can infact (as you probably know) also tune timing by reading the ground strap on the plug also... Ill find the link to some great reading when i remember where it is >.<

The heat that is caused when detonation is occuring (oreven the heat before it occurs) is enough to dis-colour the ground strap and in turn give u an indication of where the timing is, and combustion temps.

The general rule is that you want the mis-colouration to be on the 90' bend of the ground strap, if its closer the the base ring, its too hot (ie too much timing) or if its out near the end its too cold (not enough).

And not to mention there isnt really a one timing suits all either, cams, head work, valves etc etc all make it infinitly variable... motors are dynamic, not some set piece of equipment

EDIT:- found the linky link How to read Racing Spark Plugs

 

[headsmess]

i dont use gunpowder for bombs, its rate of combustion doesnt suit me....

now, something like picric acid or mercury fulminate....totally different story

reminding me that i read something about a bunch of monks(yes, monks) that tried making an engine run on gunpowder in the early days of the industrial revolution

can you imagine the carbon build up if it had worked?

lol, yes...solid info from cactus that cant be elaborated on.

 

[Cactus Jack]

Yes you can go in depth into plug reading but the stop watch never lies ... Plug reads are only as consistent as the fuel you're using ... They're only really a guide ... I never go totally off the colour of the plug ... how the engine sounds and actually performs on the track is far more important ... You want it to perform consistently for long periods ... not just put out a heap of dyno power then drop off and pack it in after a few laps or races ...

I found a link on advanced plug reading ... One guy talks about how he lost 42 hp from just 1 degree too much ignition advance ... For dirt bikes especially , where the engines can be expected to handle getting flogged all day long ... you need a safety margin due to varying operating temperatures ... so the last thing you want is to run the advance on the edge ... The same as with the jetting ... There's no point in tuning a dirt bike engine as highly as you would a drag bike engine ... and even then , drag racers run lesser states of tune until the very last race (after they've got the meeting won) ... Then they run their max tune in an attempt to break their class speed and ET records when they've got nothing to lose if the engine grenades ...

It'd be interesting to get one of those lights and the video they're talking about ...

Spark Plug Reading Secrets

 

[daimojay]

indeed cactus, and i never said soley off the plug either, but its a good guide for a quick glace at the state of tune

P.S. good read!

 

[Cactus Jack]

I just read your link Damo ... great stuff ... I've book marked it ... So how's the Z155 engine holding up ? ... Have you found any weak points yet ? ... Are the stock heads any better than the stock YX heads ? ... BTW ... the blonde wig don't suit you ... makes you look too cheap ...

 

[fiffty _boytim]

hey man hope you get it sorted as my last yx 150 was runing 16 - 37 and was pulling up the front wheel with out needing to pop the clutch and it didnt lack in acceleration of the mark either as i had it set up for short run ups for fmx

 

[daimojay]

haha cactus its a beenie, and its also cheap as for the z155's so far its a smooth motor, once i find a stock yx head to compare it with as mine is long gone, but with the longer stroke you can feel the bottom end is stronger power wise. The build and finish is alot better on these than the yx's too. Its not missed a beat so far, and ive been running it with my scut kit also = 194cc V2 with my s35... Goes very hard... Scary fast

 

[NRG]

This place still cracks me up! BUt what the "hey", it makes for good reading on a boring Monday............

 

[thump*140]

This place still cracks me up! BUt what the "hey", it makes for good reading on a boring Monday............

mate you should read the thread on edumacating motovert24... now that's grade A literature right there my friend!!

 

[daimojay]

cracks you up cause you have nfi? How bout something usefull or gtfo to be honest