Post by vvtr on Jan 2, 2012 9:28:57 GMT -5
reading 90's tuning thread with interest, it brough back some memories which ill share for your amusement!
unfortunately long before the days of digital cameras & gps so you'll have to take my word!
age 15 i was the proud owner of a suzuki ap50... like this (only red)
and was ready for my 16th birthday when i could legally ride it on the road...
after just a few weeks, while out on a ride with a few mates, it spontaneously combusted on me at a set of traffic lights and was reduced to ash
damn shame - that thing had an indicated speed of 55mph and was real fun to ride.
everyone had either an ap50, yammy fs1e, honda sl50 or gilera / garelli moped.
happy days
so, my first insurance claim, and i got one of these:
thing is, by then the law had changed... and instead of being allowed to ride a moped - 50cc with pedals, capable of 60mph, the new '16ers' had no pedals & looked like proper bikes, but were restricted to around 3bhp with a top speed of 30mph!
first thing we all did was fit a bigger front sprocket which gave tops of around 40mph with head down, downhill!
but anyway, we were all proper bikers now & it didnt matter!
unfortunately, after about 1000 miles, the oil pump failed on my new bike & it went off for warranty repairs & was away for months.
in the meantime i had a yammy dt175 dirt bike which i used to sometimes (illegally!) take out on the road.
it felt mega fast compared to the 50 so when i got my ped back i was sooo disappointed in its performance i decided to tune it a bit.
there was no internet then so most of this was trial & error.
usually error lol.
my first attempt was raising primary compression... i figured i could do this simply by filling the crankcase with oil!
all i managed to do was hydro-lock the piston and make a lot of smoke!
so off to the library i went to learn...
i decided to take my cylinder & piston to a local kart tuner - terry shepperd (he's still around!) and for £50 he ported the barrel for me - didnt actually look like he'd done much tbh.
while the cyl was away i filed away the lip on the cylinder head and ground it flat with lapping paste on a mirror...
whn my cylinder came back i had a brainwave... must have more cc's i thought.
so like a fool i decided to bore it out to the maximum oversize, thinking it would make a difference!
1.5mm oversize! YESSS.
fitted it all together and took it out on the road... OMFG the difference was incredible! wow! i was amazed.
absolutely loving it.
until.... (just like 90) a circlip came out. the pin moved over and completely trashed the bore & piston.
i was gutted. after spending money on it (£50 was a lot in 1980 lol) & i coudnt afford a new cylinder.
there weren't any bbk's then either.
so, unperturbed i went to the nearest suzuki dealer, bill pope motors, and spent hours with the guy going through all the microfiches looking for a piston with the same gudgeon pin size and pin to crown distance...
i settled on a piston from a suzuki fr80 (though i had to cut about 15mm off the skirt)
it was like suzuki's 2 stroke version of honda's popular c90.
the zr50 had a bore of 39mm which i'd increased to 40.5, but the fr80 was 46mm!!!
so off i went to a local machine shop - wilber motors (still there!) and got the barrel bored out a further 5.5mm!
i was gutted they charged me for 3 rebores lol!
the liner was now Very thin!
i also decided before i fitted it, ive nothing to lose, so i got out the drill with ordinary drill bits, and proceeded to make the ports deeper, without altering the heights etc.
then i got a length of 6mm steel rod and cut a slot in the end and filed a flat on the other end so it would grip in the drill.
while i was at wilber motors, i pinched some heavy duty linishing belt material which i tore into strips, wound through the slotted rod and there you go, got myself an adjustable flexible porting tool
(works great btw!)
i expanded and polished up the ports and thought while im at it, i'll bore out the carb too.
the standard carb was tiny - about 12mm, so i bored the venturi out to the same diameter as the slide, about 17mm and polished it mirror with solvol autosol polish.
next the exhaust, known to be a restriction, i got an off the shelf expansion pipe designed for the ap50, sawed off the header and grafted on the header off my bike,
put it all together and fired it up....
JEEEZ!!! i reckoned it to now be about 70cc, massively oversquare which should make it rev high - and did it!!!
it was extremely responsive!
very fast indeed, going off the speedo (60mph), power wheelies on take-off etc! i was made up with it!
apart from the single cable operated disc brake & drum rear lol!
next i decided to go even bigger with the carb so grafted on a carb from a kawi kh250, bored out again and polished inside...
the results were genuinely amazing.
most of my mates had progressed to 125s & 250s by this time but i was still keeping ery respectable speeds on the little suzi... clocked at over 70mph!
unfortunately, one day going down fleet lane in st.helens as 60mph i was intercepted by a large german shepard dog which totally wrote off the front end off the bike so sadly i had to let it go.
not long after, i was in a local bike shop & saw my bike for sale, all fixed up & back on the road with a sign on it saying 'a very sporty 16er'
after a while i got myself a job in a local honda dealers - tommy robb, an ex tt racer who raced with the great mike hailwood on the legendary 250/6....
& the man himself - bossman tommy, probably at the tt
i absolutely loved it, like heaven for a young biker
all i used to do apart from make tea and brush the workshop, was assemble the new rev n go 50s (mostly honda melody's, expresses etc) when they came in crates, part assembled, 2 in a crate, and deliver them, usually to hot 16yo girls lol
and when trade ins came in, it was my job to clean them up and service them, while learning the trade from the proper techs.
brilliant!
i did have some disasters lol, like one time i tried to respray the sidepanels on a silver cb250n but couldnt find an aerosol, so tried to make a spraygun with a plastic bottle... attached it to a 10 bar airline and of course it exploded, completely covering all the customers bikes in the shop with silver paint lol!
and then a rep came in selling 'ally kleen' for cleaning ally. i decided to test it on a cb550k and it absolutely destroyed the casings and forks lol, it looked ancient! not recommended.
then again on the same 550 i think, i decided to wash out the exhausts with a hose pipe, not realising half the valves would be open lol... resulting in a very severe bollocking and having to spend all weekend striping the head off the bike lol!
ah well, we learn!
so anyway at 17 i could now ride a bigger bike and although i was allowed a 250cc, i had my eye on a suzi gp125.... it looked like this when i got it
the boss let me earn it off
i had already spent weeks on it in works time, knowing it was going to be mine!
a friend over the road had the identical bike, but brand new... mine was a 'T reg, 1978 model, his was a x reg,'82.
but on the road mine was totally different... it seemed like it had another gear and was a lot more pokey.
these are a 124cc disc valve single btw...
so one rainy day we decided to strip them to see what the difference was, apart from gearing.
the difference was in the porting & cylinder head... and mine had a slightly bigger carb.
mine had an extra pair of transfer ports and 2 boost ports, plus a piston port to match, while his looked very basic.
mine had a squish type head while his was just a bowl.
me being me, i thought well, its off now, might as well...
so i took a grinder to the head to remove the lip, then files, then valve lapping paste, just like before, much to my mate's horror!
then got the slotted stick out and set to the ports, enlarging them, polishing and raising the exhaust about 1/8" with absolutely no measurements taken!
by the time id finished you could get your head in the exhaust port lol!
i decided it would be better to knife edge the ports rather than curve & chamfer them.... (which probably explains why i got through so many rings lol)
i also cut a slice off either side of the disc valve, pure guesswork. just wanted it to start opening as soon as the piston started going up the bore, and closing as soon as it started back down.
back together & on the road the results were great... very peaky with a great powerband, moved from 6-7k up to 7-9000 but it seemed the exhaust was choking it a bit so i sawed off the header and removed a thinner pipe from inside after much wiggling.
after reading more about kart tuning, i decided to chop an inch off the header & brazed it back on...
result was a bit flat under 5k but very peaky and revved well over 10,000rpm!
i remember taking it out on the road after that & racing a guy on a 250lc yammy, flipped my bike on take-off and still ended up beating him lol
(burtywood bends & the mad mile - alder lane )
before long the mains started to get a bit rumbley so i rode the bike to a crank / rebore place 30 mies away and stripped the engine outside in the carpark... got new bearings pressed in then rode it home
(i ended up a very regular customer lol and still use them now!)
realising how easy it was to strip, i took it all apart again (i'd never really seen a crank before) and i packed the balancing holes in the crank with corks soaked in 2 stroke oil (another kart trick) to raise primary compression.
didnt know about port matching at the time so it all went back together for a test.... brilliant.
a bit of vibration from the unbalanced crank but very different!
but... silly me had forgotten to attach the oil pipe from the pump and seized it after just a few miles when the assembly oil had burnt away lol.
(iirc that was the day prince charles & diana got married and we all got a free day off work!)
took it all apart again overnight and did the bearings (and big end) again and had grampian motors balance the packed crank for me so it didnt vibe so much.
i rode it like that for months, racing everything on the road lol it would easily top 110mph which was as good if not faster than most of the 250s and a lot of the IL4s like honda 400/4, superdreams etc...
loved it to bits. but wanted more, even though it only did about 15mpg lool!
so i got myself a carb off a yz400 crosser and shoehorned it into the side casing... had to leave the lid off so the airbox got junked, just ran a gauze over the end of it to keep flies & small children from getting sucked in lol!
it developed a 2nd power band, 1st from the original redline at 8k to 10k, then again it came on song about 12- 13000rpm but got crazy clutch slip.
i ended up replacing the stock clutch springs with valve springs from a mini engine
standard max rpm on the gp125 was 8500 iirc
what an awesome bike that was lol!
so much so that i entered it in 'proddy races' over 2 seasons and thoroughly enjoyed it.
by that time it was unrecognisable as a gp125, with a fibreglass fairing, single seat, clip on bars, running premix etc...
it finally died on a fast run up the m6 motorway when the box went.
the oil drain plug on it was also the gearbox detent bolt that holds it in gear with a little ball & spring, which had got lost a long time since... it was ok when accelerating but in top gear i had to hold it in gear with my boot under the gear lever lol... id ridden it like that for ages, but this time it dropped out of top gear at daft mph & without thinking i dropped it down a gear & mashed the box totally.
i limped home on it stuck in 3rd gear & decided enough was enough.
the stress of going through a piston every week (literally) and rebearing the crank every month had took its toll on me and i decided to sell it, or what was left of it.
the lad who bought it just used the 125 barrel & head with a new piston and put it on his otherwise stock gp100.
i was left with a windowledge full of pistons with varying degrees of melting. smashed gudgeon pin holes, holed crowns, bent conrods etc as souvenirs
but anyway.. point is... 2 stroke tuning.. its a very contageous virus and there is no known cure
*oh forgot to add... just as an experiment, on the 125, i got a cyllinder & head off an old aircooled reed valve inducted suzuki rm125 motocrosser and it fitted straight on.... this was an incredible 9 port barrel with ridiculously large ports... but the main thing was, i now had a yz400 carb sticking out the side casing AND the rm125 carb feeding through the reeds on top lol.
you dont see that very often lol, in fact id never seen it done before or since, but what an awesome mod lol!
unfortunately long before the days of digital cameras & gps so you'll have to take my word!
age 15 i was the proud owner of a suzuki ap50... like this (only red)
and was ready for my 16th birthday when i could legally ride it on the road...
after just a few weeks, while out on a ride with a few mates, it spontaneously combusted on me at a set of traffic lights and was reduced to ash
damn shame - that thing had an indicated speed of 55mph and was real fun to ride.
everyone had either an ap50, yammy fs1e, honda sl50 or gilera / garelli moped.
happy days
so, my first insurance claim, and i got one of these:
thing is, by then the law had changed... and instead of being allowed to ride a moped - 50cc with pedals, capable of 60mph, the new '16ers' had no pedals & looked like proper bikes, but were restricted to around 3bhp with a top speed of 30mph!
first thing we all did was fit a bigger front sprocket which gave tops of around 40mph with head down, downhill!
but anyway, we were all proper bikers now & it didnt matter!
unfortunately, after about 1000 miles, the oil pump failed on my new bike & it went off for warranty repairs & was away for months.
in the meantime i had a yammy dt175 dirt bike which i used to sometimes (illegally!) take out on the road.
it felt mega fast compared to the 50 so when i got my ped back i was sooo disappointed in its performance i decided to tune it a bit.
there was no internet then so most of this was trial & error.
usually error lol.
my first attempt was raising primary compression... i figured i could do this simply by filling the crankcase with oil!
all i managed to do was hydro-lock the piston and make a lot of smoke!
so off to the library i went to learn...
i decided to take my cylinder & piston to a local kart tuner - terry shepperd (he's still around!) and for £50 he ported the barrel for me - didnt actually look like he'd done much tbh.
while the cyl was away i filed away the lip on the cylinder head and ground it flat with lapping paste on a mirror...
whn my cylinder came back i had a brainwave... must have more cc's i thought.
so like a fool i decided to bore it out to the maximum oversize, thinking it would make a difference!
1.5mm oversize! YESSS.
fitted it all together and took it out on the road... OMFG the difference was incredible! wow! i was amazed.
absolutely loving it.
until.... (just like 90) a circlip came out. the pin moved over and completely trashed the bore & piston.
i was gutted. after spending money on it (£50 was a lot in 1980 lol) & i coudnt afford a new cylinder.
there weren't any bbk's then either.
so, unperturbed i went to the nearest suzuki dealer, bill pope motors, and spent hours with the guy going through all the microfiches looking for a piston with the same gudgeon pin size and pin to crown distance...
i settled on a piston from a suzuki fr80 (though i had to cut about 15mm off the skirt)
it was like suzuki's 2 stroke version of honda's popular c90.
the zr50 had a bore of 39mm which i'd increased to 40.5, but the fr80 was 46mm!!!
so off i went to a local machine shop - wilber motors (still there!) and got the barrel bored out a further 5.5mm!
i was gutted they charged me for 3 rebores lol!
the liner was now Very thin!
i also decided before i fitted it, ive nothing to lose, so i got out the drill with ordinary drill bits, and proceeded to make the ports deeper, without altering the heights etc.
then i got a length of 6mm steel rod and cut a slot in the end and filed a flat on the other end so it would grip in the drill.
while i was at wilber motors, i pinched some heavy duty linishing belt material which i tore into strips, wound through the slotted rod and there you go, got myself an adjustable flexible porting tool
(works great btw!)
i expanded and polished up the ports and thought while im at it, i'll bore out the carb too.
the standard carb was tiny - about 12mm, so i bored the venturi out to the same diameter as the slide, about 17mm and polished it mirror with solvol autosol polish.
next the exhaust, known to be a restriction, i got an off the shelf expansion pipe designed for the ap50, sawed off the header and grafted on the header off my bike,
put it all together and fired it up....
JEEEZ!!! i reckoned it to now be about 70cc, massively oversquare which should make it rev high - and did it!!!
it was extremely responsive!
very fast indeed, going off the speedo (60mph), power wheelies on take-off etc! i was made up with it!
apart from the single cable operated disc brake & drum rear lol!
next i decided to go even bigger with the carb so grafted on a carb from a kawi kh250, bored out again and polished inside...
the results were genuinely amazing.
most of my mates had progressed to 125s & 250s by this time but i was still keeping ery respectable speeds on the little suzi... clocked at over 70mph!
unfortunately, one day going down fleet lane in st.helens as 60mph i was intercepted by a large german shepard dog which totally wrote off the front end off the bike so sadly i had to let it go.
not long after, i was in a local bike shop & saw my bike for sale, all fixed up & back on the road with a sign on it saying 'a very sporty 16er'
after a while i got myself a job in a local honda dealers - tommy robb, an ex tt racer who raced with the great mike hailwood on the legendary 250/6....
& the man himself - bossman tommy, probably at the tt
i absolutely loved it, like heaven for a young biker
all i used to do apart from make tea and brush the workshop, was assemble the new rev n go 50s (mostly honda melody's, expresses etc) when they came in crates, part assembled, 2 in a crate, and deliver them, usually to hot 16yo girls lol
and when trade ins came in, it was my job to clean them up and service them, while learning the trade from the proper techs.
brilliant!
i did have some disasters lol, like one time i tried to respray the sidepanels on a silver cb250n but couldnt find an aerosol, so tried to make a spraygun with a plastic bottle... attached it to a 10 bar airline and of course it exploded, completely covering all the customers bikes in the shop with silver paint lol!
and then a rep came in selling 'ally kleen' for cleaning ally. i decided to test it on a cb550k and it absolutely destroyed the casings and forks lol, it looked ancient! not recommended.
then again on the same 550 i think, i decided to wash out the exhausts with a hose pipe, not realising half the valves would be open lol... resulting in a very severe bollocking and having to spend all weekend striping the head off the bike lol!
ah well, we learn!
so anyway at 17 i could now ride a bigger bike and although i was allowed a 250cc, i had my eye on a suzi gp125.... it looked like this when i got it
the boss let me earn it off
i had already spent weeks on it in works time, knowing it was going to be mine!
a friend over the road had the identical bike, but brand new... mine was a 'T reg, 1978 model, his was a x reg,'82.
but on the road mine was totally different... it seemed like it had another gear and was a lot more pokey.
these are a 124cc disc valve single btw...
so one rainy day we decided to strip them to see what the difference was, apart from gearing.
the difference was in the porting & cylinder head... and mine had a slightly bigger carb.
mine had an extra pair of transfer ports and 2 boost ports, plus a piston port to match, while his looked very basic.
mine had a squish type head while his was just a bowl.
me being me, i thought well, its off now, might as well...
so i took a grinder to the head to remove the lip, then files, then valve lapping paste, just like before, much to my mate's horror!
then got the slotted stick out and set to the ports, enlarging them, polishing and raising the exhaust about 1/8" with absolutely no measurements taken!
by the time id finished you could get your head in the exhaust port lol!
i decided it would be better to knife edge the ports rather than curve & chamfer them.... (which probably explains why i got through so many rings lol)
i also cut a slice off either side of the disc valve, pure guesswork. just wanted it to start opening as soon as the piston started going up the bore, and closing as soon as it started back down.
back together & on the road the results were great... very peaky with a great powerband, moved from 6-7k up to 7-9000 but it seemed the exhaust was choking it a bit so i sawed off the header and removed a thinner pipe from inside after much wiggling.
after reading more about kart tuning, i decided to chop an inch off the header & brazed it back on...
result was a bit flat under 5k but very peaky and revved well over 10,000rpm!
i remember taking it out on the road after that & racing a guy on a 250lc yammy, flipped my bike on take-off and still ended up beating him lol
(burtywood bends & the mad mile - alder lane
)before long the mains started to get a bit rumbley so i rode the bike to a crank / rebore place 30 mies away and stripped the engine outside in the carpark... got new bearings pressed in then rode it home
(i ended up a very regular customer lol and still use them now!)
realising how easy it was to strip, i took it all apart again (i'd never really seen a crank before) and i packed the balancing holes in the crank with corks soaked in 2 stroke oil (another kart trick) to raise primary compression.
didnt know about port matching at the time so it all went back together for a test.... brilliant.
a bit of vibration from the unbalanced crank but very different!
but... silly me had forgotten to attach the oil pipe from the pump and seized it after just a few miles when the assembly oil had burnt away lol.
(iirc that was the day prince charles & diana got married and we all got a free day off work!)
took it all apart again overnight and did the bearings (and big end) again and had grampian motors balance the packed crank for me so it didnt vibe so much.
i rode it like that for months, racing everything on the road lol it would easily top 110mph which was as good if not faster than most of the 250s and a lot of the IL4s like honda 400/4, superdreams etc...
loved it to bits. but wanted more, even though it only did about 15mpg lool!
so i got myself a carb off a yz400 crosser and shoehorned it into the side casing... had to leave the lid off so the airbox got junked, just ran a gauze over the end of it to keep flies & small children from getting sucked in lol!
it developed a 2nd power band, 1st from the original redline at 8k to 10k, then again it came on song about 12- 13000rpm but got crazy clutch slip.
i ended up replacing the stock clutch springs with valve springs from a mini engine
standard max rpm on the gp125 was 8500 iirc
what an awesome bike that was lol!
so much so that i entered it in 'proddy races' over 2 seasons and thoroughly enjoyed it.
by that time it was unrecognisable as a gp125, with a fibreglass fairing, single seat, clip on bars, running premix etc...
it finally died on a fast run up the m6 motorway when the box went.
the oil drain plug on it was also the gearbox detent bolt that holds it in gear with a little ball & spring, which had got lost a long time since... it was ok when accelerating but in top gear i had to hold it in gear with my boot under the gear lever lol... id ridden it like that for ages, but this time it dropped out of top gear at daft mph & without thinking i dropped it down a gear & mashed the box totally.
i limped home on it stuck in 3rd gear & decided enough was enough.
the stress of going through a piston every week (literally) and rebearing the crank every month had took its toll on me and i decided to sell it, or what was left of it.
the lad who bought it just used the 125 barrel & head with a new piston and put it on his otherwise stock gp100.
i was left with a windowledge full of pistons with varying degrees of melting. smashed gudgeon pin holes, holed crowns, bent conrods etc as souvenirs
but anyway.. point is... 2 stroke tuning.. its a very contageous virus and there is no known cure
*oh forgot to add... just as an experiment, on the 125, i got a cyllinder & head off an old aircooled reed valve inducted suzuki rm125 motocrosser and it fitted straight on.... this was an incredible 9 port barrel with ridiculously large ports... but the main thing was, i now had a yz400 carb sticking out the side casing AND the rm125 carb feeding through the reeds on top lol.
you dont see that very often lol, in fact id never seen it done before or since, but what an awesome mod lol!
