Yamaha Genuine Racing Cam
- Thread starter charge
- Start date
joel said:
on my stock engine, i shaved off 1mm on my cylinder block
but still the top and bottom gasket is still there.
after 5000km so far no valve piston damage..
engine runs fast!!!!
I love high compression engines!
bro care to show how did you compute the compression ratio
on this thread
http://www.yamahat135.com/forum/viewtopic.php?t=714
Hi Traxxas, if u have removed 1mm on your cylinder block on a 57mm vixion block, then ur new compression is ratio is,traxxas-modifier said:
formula - cc+Vc/Vc
Vc - Volume of combustion chamber
U have removed 1mm on the cylinder block, so the new combustion chamber volume is 13.35
Stock is 15.9cc
Therefore - 149.7+13.35/13.35 = 12.2
So 12.2:1 is ur new compression ratio.
But, I'm surprised how is it that your valves are not banging, have u modified the piston pockets?
I'm also running top and bottom gaskets.
No buddy. 3-bond sealer will remain in place as long as u dont remove the block. It will seal really well.charge said:
What I mentioned is static compression, not dynamic.
Dynamic will be much higher.
@Haen - From what i've seen anything more than 0.65mm will give a valve bang.
I have a feeling that traxxas bike is running a retarded cam timing. Only then it can miss the piston. Coz the exhaust valve pocket on the piston is 0.3mm deep. It might be barely missing the piston or even touching a bit at high revs, but going un-noticed.
And again if u remove 1mm on the block, there is a possibility of the piston banging the head squish too.
I'm confused whats his set-up.
The piston SHOULD be modified then.
On my engine, I've removed material off the cylinder head too, along with the cylinder block. So it avoids head bang issues. Bit valve pockets have to be cut 1.5mm deep.
My comp ratio is at 12.5:1
@joel : yup.. i think u r right.. maybe mr. Traxx is phasing the cam in retarded mode.. since i've done it myself but on advancing mode.. i won't go that brave as mr. traxx.. still playing safe by removing the lower gasket only.. therefore i can get back to standard setup if needed.. but sometimes i wonder whether threebond is sufficient to prevent heat spreading to the crankcase section.. any comment from joel or mr. Stroker.. i want to experiment with lower block 0.5 mm later..
from what i heard.. higher comp has side effects like heat and more vibration.. but if all cohesively tied together like stroker always said.. who knows..
from what i heard.. higher comp has side effects like heat and more vibration.. but if all cohesively tied together like stroker always said.. who knows..
haha, I'll take all of you guys suggestions here!
This round, I am going to revert back to stock camshaft with retarded timing (I suppose it shifts powerband to higher rpm). Still awaiting YYPang valvespring from mr Lc-motorspeed.
And I've my CDi relayed, the 2 small hoses removed from the airbox and the spark plug grounded. hehehe
This round, I am going to revert back to stock camshaft with retarded timing (I suppose it shifts powerband to higher rpm). Still awaiting YYPang valvespring from mr Lc-motorspeed.
And I've my CDi relayed, the 2 small hoses removed from the airbox and the spark plug grounded. hehehe
lc-motospeed
Super Veteran
@charge
ur valve springs will b delivered by tuesday if everything goes smoothly like stock availability =)
ur valve springs will b delivered by tuesday if everything goes smoothly like stock availability =)
lc-motospeed
Super Veteran
hu? me? have i provided u any aid? haha... well, if u're referring to me then u r welcomed, if not then sorry =) =P >< haha
lc-motospeed
Super Veteran
well, good to hear tat... by the way, here's ur valve springs... i'll b sending it via pos laju by 2moro 4pm
Attachments
Hi Hean,
I have a query on the cam now.
I have again installed that fat cam. It looks like a 270deg cam to me. Power is pretty bad in low revs, infact feels really weak between 4-5k rpm. Before and after tha is fine. From 7000rpm it wakes up real hard. But the engine is very noisy. I have clearance of .10 for In and Ext.
Just wondering what experiences you have on this? Will the valves + springs wear out too soon using this cam. I have a race this weekend, just need to take part this time.
I have richened the mixture by changing the AFR setting.
How can the engine be made quiter? Any idea to gain some lost low-end punch.
I have a query on the cam now.
I have again installed that fat cam. It looks like a 270deg cam to me. Power is pretty bad in low revs, infact feels really weak between 4-5k rpm. Before and after tha is fine. From 7000rpm it wakes up real hard. But the engine is very noisy. I have clearance of .10 for In and Ext.
Just wondering what experiences you have on this? Will the valves + springs wear out too soon using this cam. I have a race this weekend, just need to take part this time.
I have richened the mixture by changing the AFR setting.
How can the engine be made quiter? Any idea to gain some lost low-end punch.