General AM6 questions (reliability, tuning, etc)

[Akim Vasiliev]

Hello all,

I am not an Aprilia owner but I am thinking of buying a motorcycle that comes with a Minarelli AM6 engine, and because there seem to be a few very knowledgeable people on this forum in regards to it, I figured I would ask my questions here. I hope you guys don't mind!

The motorcycle in question is a CPI Supermoto50. I'm approximately 180cm in height and about 60 kilos, before this bike I have owned various motocross bikes (Yamaha YZ80, KTM 300 MXC), but never had something road legal.

Anyway, my questions are pretty simple.

1. In totally stock trim, how reliable is the AM6 engine? What sort of RPM's can it run continuously without damaging itself? What sort of fuel should you run in it (I seem to remember the CPI requiring 95 octane, supposedly it has 12:1 compression ratio stock, but that seems a little high for a stock motorbike).

2. Is there are danger in converting the bike to premix? I know some older Japanese 2-strokes had oil injection that actively oiled the crank bearings, and if you premixed them, that would drastically lower the life span of the crank.

3. Is it possible to tune the engine for better midrange power? I am planning on riding mostly offroad with it (forests etc) but I need to retain road-riding ability to drive from my garage to the woods first, and not get pulled over by the police. At what displacement (50cc, 70cc, 80cc, +++) should you replace which parts, meaning what else do I need to upgrade if I'm planning on installing, for example, a 75cc big bore kit and exhaust?

Thanks in advance for your time!

[Josh_rs]

not sure about the engines, but i know those cpi supermotos have bad electrical problems...

[chrism15]

Hello all,

I am not an Aprilia owner but I am thinking of buying a motorcycle that comes with a Minarelli AM6 engine, and because there seem to be a few very knowledgeable people on this forum in regards to it, I figured I would ask my questions here. I hope you guys don't mind!

The motorcycle in question is a CPI Supermoto50. I'm approximately 180cm in height and about 60 kilos, before this bike I have owned various motocross bikes (Yamaha YZ80, KTM 300 MXC), but never had something road legal.

Anyway, my questions are pretty simple.

1. In totally stock trim, how reliable is the AM6 engine? What sort of RPM's can it run continuously without damaging itself? What sort of fuel should you run in it (I seem to remember the CPI requiring 95 octane, supposedly it has 12:1 compression ratio stock, but that seems a little high for a stock motorbike).

2. Is there are danger in converting the bike to premix? I know some older Japanese 2-strokes had oil injection that actively oiled the crank bearings, and if you premixed them, that would drastically lower the life span of the crank.

3. Is it possible to tune the engine for better midrange power? I am planning on riding mostly offroad with it (forests etc) but I need to retain road-riding ability to drive from my garage to the woods first, and not get pulled over by the police. At what displacement (50cc, 70cc, 80cc, +++) should you replace which parts, meaning what else do I need to upgrade if I'm planning on installing, for example, a 75cc big bore kit and exhaust?

Thanks in advance for your time!

if it is the same engine as the Rs 50 then its a good little engine, easy to work on, good amount of power for its size, reliability i wud say is maybe its fall BUT if its maintained well then it will be fine

what rpms can it run at safely: WARM THE BIKE FIRST, then as long as you dont drive it with the revs bouncing over 12000 everywhere then it will be fine just make sure its warmed up first and rev away

converting to premix: perfectly possible and some do it but for road use just keep the oil tank , pump ect and if u want extra confidence then put 1:100 in the tank and keep the carb clean

to get more midrange, two easyisest ways are proberbly, gear it down a few teeth on ear/front sprocket but most of all then put a race exhaust on it

what wud u need to upgrade with a bore kit:
cylinder - 70cc/75cc/80cc
race/endurance crank - doppler er1 is GOOD
get a exhaust thats more suited to bigger cc cylinder
reeds - 0.30mm/ 0.35mm / 0.40mm tops
bigger carb 19.5mm/ 21mm
heavy duty clutch , just get stronger springs and plates to make it cheaper
and if u want to go a lil over the top then a heavy duty chain haha

[RS_Patrick]

CPI engine is not a AM-6 engine... its a chinese copy (why design something your self if you can just copy it?)

1: see above, i dont know about that, but best feul to use is Shell V-Power.

2: For Road use Premix is a bad idea as the mix ratio is 1:33 max from the oil pump and you would need to premix 1:35 wich can cause problems wen running half throttle/midrange rpm and lower.
Its best to run the oilpump and add premix 1:100 aditional trough the feul.

3: its a chinese copy, AM-6 parts do not fit, and good luck finding parts for the CPI engine... i dont know any after market manufacturer that makes parts for them.

[chrism15]

CPI engine is not a AM-6 engine... its a chinese copy (why design something your self if you can just copy it?)

1: see above, i dont know about that, but best feul to use is Shell V-Power.

2: For Road use Premix is a bad idea as the mix ratio is 1:33 max from the oil pump and you would need to premix 1:35 wich can cause problems wen running half throttle/midrange rpm and lower.
Its best to run the oilpump and add premix 1:100 aditional trough the feul.

3: its a chinese copy, AM-6 parts do not fit, and good luck finding parts for the CPI engine... i dont know any after market manufacturer that makes parts for them.

dont know if im right here but ddidnt u put a post up maybe even yrs ago about a cpi engine that was same as the Rs50 am6 but was a prototype?

[RS_Patrick]

Yes, that was a 6 speed 2 stroke injection engine, they never took it in production as far as i know, but at the time i did not know that the CPI engine was a Copy of a Minarelli AM-6.

I never worked on those CPI geared mopeds, but where they do sell them i had a close look and the dealer also said that its a copy (but asured me it was really good quality stuff..........)

[chrism15]

Yes, that was a 6 speed 2 stroke injection engine, they never took it in production as far as i know, but at the time i did not know that the CPI engine was a Copy of a Minarelli AM-6.

I never worked on those CPI geared mopeds, but where they do sell them i had a close look and the dealer also said that its a copy (but asured me it was really good quality stuff..........)

oh right, bet it wud be more reliable and perform better if it was fuel injected , shame they never put it in production

[Akim Vasiliev]

Patrick: I was lead to believe that the CPI was made in Taiwan, not China. Taiwan has fairly good build quality and lots of smaller Japanese bikes are at least partly made in Taiwan (and have been for a while now) so I suppose the build quality can't be TOO bad.

Judging from everything I've read, AM6 parts fit just fine on the CPI engine. There have been people here who have apparently had success fitting Polini and Barikit parts to the CPI. I don't know from first hand experience though, so that's all I can say.

However, given all the extra costs of tuning and increasing power (big bore kit, stronger crank, performance exhaust = at least 50% of the cost of the bike itself), I'm thinking of just getting something like a DT125R and not even bothering with the 50cc bikes...

Chris: Thanks for the quick answer, I really appreciate it. We'll see if I end up using the info you've posted.

[mumbl3s]

has anyone else notice how often this kinda question is asked (not about the cpi but about upgrading to a BBK and the parts need to be replaced) i think we need a sticky on BBK's

[chrism15]

has anyone else notice how often this kinda question is asked (not about the cpi but about upgrading to a BBK and the parts need to be replaced) i think we need a sticky on BBK's

!! good idea - send one of the mods a Private message and start a thread (ask him to make it a sticky in the tech section but dont lock it - keep it open so people can add to it whenever better parts ect come in or better methods images yano)

@ akim vasileiv - no problem pal , and sorry u have confused me now: do you want to FIT a am6 engine into a cpi or are you saying that the cpi itself HAS a am6 engine and you want to tune it?

a DTR 125 wud be a good lil bike, have u seen yamaha"s wr 125? thats similar BUT if you want something thats a 125cc but lethal then get a aprilia MX/SX/RX 125 coz their two stroke but motocross style bikes that are road legal able to reach speeds of 100mph as they have the same engine as the aprilia Rs 125 but coz of the style bike (motocross frame) its alot lighter and makes it want to wheelie easy

but if you still want to get the cpi then go for it and if you can get hold of parts for it then get a nice 70cc-80cc cylinder kit, doppler er1 crank if availiable and a 19.5mm - 21mm carb and a heavy duty clutch and adapt it to your style of riding through forests and twisty roads ect

[RS_Patrick]

I dont know about fitting AM-6 parts onto a CPI, The Parts Do Not Fit!!! (atleast not with out some modifications made) I read that on several forums, for that reason, and for the reason that original CPI engine parts are really hard to get, a lot of people swap the CPI Engine for a Minarelli AM-6.

Taiwan is a province of China according to the Chinese

If you want to go Ofroad your better off buying a Yamaha DT50R or DT125R, or atleast a true off the road model and not a Super Motard

Yamaha DT50R uses a Minarelli AM-6 engine, loads of parts for them to get.

But i dont know the terain your gonna drive in (underground in the forest) but a bit more power like a 125cc 2 stroke or 250cc 4 stroke might be verry usefull if its really rugged sand or mud.

Derbi engine or AM-6 engine are ok for just dirt roads with a few centimeters of mud and sand on them, but other than that you need a bit more power to keep going trough deeper mud and loose sand.

[Akim Vasiliev]

@ akim vasileiv - no problem pal , and sorry u have confused me now: do you want to FIT a am6 engine into a cpi or are you saying that the cpi itself HAS a am6 engine and you want to tune it?

a DTR 125 wud be a good lil bike, have u seen yamaha"s wr 125? thats similar BUT if you want something thats a 125cc but lethal then get a aprilia MX/SX/RX 125 coz their two stroke but motocross style bikes that are road legal able to reach speeds of 100mph as they have the same engine as the aprilia Rs 125 but coz of the style bike (motocross frame) its alot lighter and makes it want to wheelie easy

but if you still want to get the cpi then go for it and if you can get hold of parts for it then get a nice 70cc-80cc cylinder kit, doppler er1 crank if availiable and a 19.5mm - 21mm carb and a heavy duty clutch and adapt it to your style of riding through forests and twisty roads ect

So far most of the people I've spoken to have said that the CPI has a copy of the Minarelli AM6, and that AM6 parts fit on it without modification.

If I'm going to buy a 125, then I might as well get a full size enduro like a CRM250 or KDX250, in which case I wouldn't really even consider the 125s (here in Russia, it's either a 50cc bike, or a full size one with no engine restriction, there's no middle ground like you apparently have in the UK).

I'm thinking about the CPI, there's a few other bikes I could possibly get like the GasGas 50SM Rookie, Beta RR, Kawasaki KSR, Honda CRM, etc. My budget basically allows me to get either a more or less new CPI, or a used Japanese moped like the KSR or CRM.

The KSR is a little small for me, uses scooter-sized tires but could be fun, the CRM uses standard kid's motocross sized wheels (17" and 14") and is the "best" woods-oriented bike in it's class (but it's hard to find one in good shape here in Russia). The GasGas sounds interesting but I'm afraid it'll be hard to find parts for it. Not sure about the Beta, not really considering it as a serious contender.

I dont know about fitting AM-6 parts onto a CPI, The Parts Do Not Fit!!! (atleast not with out some modifications made) I read that on several forums, for that reason, and for the reason that original CPI engine parts are really hard to get, a lot of people swap the CPI Engine for a Minarelli AM-6.

Taiwan is a province of China according to the Chinese

I have heard from several owners of CPI Supermotos that they easily fitted Minarelli AM6 big bore kits, etc, to their machines.

I'm not totally set on getting the CPI, of course, it's just one of the more easily available bikes I can get (mainly because the guy selling it happens to live in the same town as my girlfriend).

Taiwan is a province of China only according to the Chinese government, the most countries recognize that it's a separate country. Also, most bicycles, even very high quality and expensive ones, are made in Taiwan. I trust Taiwan a lot more than China, that's just my opinion, though.

[chrism15]

seems the cpi is the way to go for you pal or put more money in and get a 250

[RS_Patrick]

The Taiwan bit was a joke mate, thats why i said according to the Chinese, but CPI Motors is based in China, not Taiwan, look it up if you dont believe me.

CPI only produces half the power output of a AM-6 powered bike, the parts Do Not Fit, yeah you can get the cilinders on there but the ports dont line up, but even worse, the Stroke is less (37,5mm compaired to 39mm on the AM-6), and you can not get a AM-6 crank in there, that totaly wont fit.
So yeah it will run, but produce a lot of power? No.

[Akim Vasiliev]

The Taiwan bit was a joke mate, thats why i said according to the Chinese, but CPI Motors is based in China, not Taiwan, look it up if you dont believe me.

CPI only produces half the power output of a AM-6 powered bike, the parts Do Not Fit, yeah you can get the cilinders on there but the ports dont line up, but even worse, the Stroke is less (37,5mm compaired to 39mm on the AM-6), and you can not get a AM-6 crank in there, that totaly wont fit.
So yeah it will run, but produce a lot of power? No.

Patrick, the official CPI site gives the SM50 engine bore/stroke as 40mm x 39.2mm. Are you sure you're not looking at some first-year model information that has been long out of date? Source: http://www.cpi-motor.com.tw/eng/sm.htm

Also yes, they have a factory in China, but they are based in Taiwan as evidenced by the .tw domain name. So far you're the only one who's said they were PRC based, just saying.

I understand you don't like the CPI for whatever reason. Can you tell me anything about the GasGas Rookie 50 Supermoto, and the Derbi Senda?

Thanks for the answers! Interesting hearing somone else's opinion!