hebo manston \ polini evo???

nrg69

New 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

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

New 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

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

New 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

New 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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