t5 - hp4?

firstly does an hp4 flywheel fit a t5 - some say it does others disagree and if it does is it worth fitting? ive heard you lose some of the electrical power.

i dont think they fit the early t5’s but not entirely sure i think they changed the cone shape,the lights are a tad dimmer coz the magnets arent as big in it but fuck me theyre worth it

stroud valleys(midnight hour)sc est 1984

thanks doc - i was hoping you would understand the problem - looks like i will just have to lay off the throttle a little in the lower gears - i’m just so used to giving her a good thrashing - so for a quick fix downsize the jets to 48/125? they are the ones i have sitting around

either that or downsize main jet and convert to a powerjet setup pre-venturi like the mikuni that way the mass of air youre flooding into the engine will be full of a mist of fuel.gain a horse power and about 300rpm onto the top of your revs.like i say the dellorto is a mediocre carb that is prone to bogging like the amal so an alternative would be better.i never trusted jap carbs on italian engines till i tried it and set it up now a convert for life.one concern is that by using your smaller jets you will be using even more air to fuel mixture

stroud valleys(midnight hour)sc est 1984

Did the hp-4 fit? I thought the taper would be to wide?
The standerd T5 flywheel is lightened,well, lighter than a p200,as I use the T5 flywheels on p2’s, just change the boss I think lightening the flywheel does weaken the fins as they cut the meatal underneath the flywheel[:)]

the lag you describe in 1st and 2nd domsmudge is because with the light flywheel and big carb the engine doesnt have to work at all to pull the low gearing and you are putting gallons of fresh air into the crank housing with the 30mm carb so in effect its flooding the motor with air and is unable to process it.hit 3rd and the engine then has to work so the crank and barrel are full of fuel air mix that has to process itself to propell the gearing i.e the engine is working efficiently.the first two gears move the gas so easily and quickly that with all the air flow you get no crank housing compression which shifts the gas up into the ports to make the old girl breathe.carb and jets seem a bit big so if you want better low to mid range grunt go down to a 28mm or for better all round use the pwk type 28/30 oval bore carb from scootrs.com.about £45-50 and beats any delorto .the oval bore creates a smaller diameter inlet for bottom end but opens to a bigger 30mm inlet for full tilt balls out riding

stroud valleys(midnight hour)sc est 1984

thanks doc
next question - how should i set the timing?

standard t5 mark is 16 degrees, px 125 is 18 degrees (IT)

have you got a hp4 flywheel on yet, if so what is it like. or am i best getting my standard 1 lightend.

rich - i have it fitted - seems to help 3rd/4th gear gap and top end a little.im still getting dialed in though - dont know how to describe it really but when accelerating gets to 1/2 throttle in both 1st and second and stops accelerating and have to change up- i guess its a carb problem - perhaps vespa doctor can help .i have 51 idle and 132 main (mallossi 172,scorpion ,dellorto 30 and the quick action throttle conversion)

the hp4 fits - my engine is 1990 - i dont think they fit the earlier ones.i didnt realise the t5 was lighter than p2 until i had removed it - had i known this i might not have bothered changing it ,think its probably more helpful on a p2 - like i said does make some difference but not totally tuned in so i cant really tell yet

its ok to leave it on the timing mark but as it’ll be revving the tits off itself swing the stator round clockwise till it stops at the end of the cutouts.standard timing mark is 18 degrees btdc and fully round is approx 16 degrees btdc so a little cooler running

stroud valleys(midnight hour)sc est 1984