hebo manston \ polini evo???

nrg69

Well-Known Member
hallo bitte ich Sie ein, was. Sie haben Foto des Hebo manston? Ich möchte es am polini evo anbringen, das ich kann?


hi I want to ask you a question...
have you any photos of hebo maston head?
i want use it on my polini evo!!!
 
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Browni

B.A.T tuning
nrg69 said:
hallo bitte ich Sie ein, was. Sie haben Foto des Hebo manston? Ich möchte es am polini evo anbringen, das ich kann?


hi I want to ask you a question...
have you any photos of hebo maston head?
i want use it on my polini evo!!!

This is a Hebo Manston 70 cc Piaggio cylinder head, but you can't use it for you evo without some modifications, the dimension are different! I have both head!







 

roost

Well-Known Member
I don't think brass is a good idea. Removing heat from the combustion chamber = removing power. However it's also questionable if there is an cooling improvement, since yes brass conducts heat better than aluminium, but aluminium collects heat better from the surrounding gasses.
I think on the head, the squish zone must be slightly rough, while the combustion cup should be polished. But those are just details.
 

BuEn

Danish Tuner
...

I thought about changing my regular head on my Hebo Manston Replica to a quish band head fra a manston kit.
Would that give any significant power change to my cilinder?
 

tiba_karotsu

OVERREV TUNING
Hebo has a higher CR than most cilinder kits (17:1) so if used with appropriate race fuel should give a nominal hp increase at peak, it's easier to machine the head with a flat squishband, this type of head is utilized by 125 & 250 GP machines. i would also like to convert to flat squish band.
 

Browni

B.A.T tuning
tiba_karotsu said:
Hebo has a higher CR than most cilinder kits (17:1) so if used with appropriate race fuel should give a nominal hp increase at peak, it's easier to machine the head with a flat squishband, this type of head is utilized by 125 & 250 GP machines. i would also like to convert to flat squish band.

Yes the theoretical compression ratio is:

CR= 17:01 if squish clearance is 0,5 mm
CR= 15,8:1 if squish clearance is 0,7 mm

So min 105-107 octane race fuel or 100/130 Avgas (100 LL) is recommended for the higher CR!
 
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nrg69

Well-Known Member
the external dimension is the same of polini??
i think so..

for the internal there isn't problem, i will work on combustion camber.

i search an hebo head because i can't find a vhm head for polini evo...
and original evo head is shit...
 

Browni

B.A.T tuning
nrg69 said:
the external dimension is the same of polini??
i think so..

for the internal there isn't problem, i will work on combustion camber.

i search an hebo head because i can't find a vhm head for polini evo...
and original evo head is shit...


As I said the outer dimensions are different too!
 

roost

Well-Known Member
I don't like high CR. High CR increases power in the midrange, while a lower CR will improve peak power.
Anyways the real CR in a 2stroke is a highly dinamic thing. If the combustion chamber has more volume (lower geometrical CR), this means also that a greater quantity of mixture will fill the cylinder. Now add the pipe suction/compression waves and the confusion is total.
Next thing I'm going to try on my racer is relatively low geometrical CR, but with powerfull exhaust pulses.
 

nrg69

Well-Known Member
cazz..... quindi anche le esterne sn diverse...

tnx browni, are you really sure that outer is different?? :)

max tedeschi order for me the vhm heads, but it never arrived....

i think that the cause is the transfer of the vhm in the new company.
there will be to wait a lot of time...
but my engine can't waitttttttt
 

nrg69

Well-Known Member
cazz..... quindi anche le esterne sn diverse...

tnx browni, are you really sure that outer is different?? :)

max tedeschi order for me the vhm heads, but it never arrived....

i think that the cause is the transfer of the vhm in the new company.
there will be to wait a lot of time...
but my engine can't waitttttttt
 
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