How much compression do you have with standard head and RockSolidEngines Billet Head

[AussieSteve]

Hi Steve
Does your engine actually run with the billet head.

Yep, no problems, except turning it over for starting. I had a couple of rides with the billet head before I fitted the shift kit. Fell on my head on the last ride, but that wasn't the head's fault. I had no problem starting it then, because I could 'bump' start, using momentum, after pedalling up to speed.
The shift kit is another matter, (I saw your thread on gearing), I can kick it hard enough, on the stand, to start it, but I haven't done it yet.
It's still in my lounge-room, waiting for the rain to stop, so there isn't even fuel in the carb yet - the best I could do was the compression test.

In my case the billet head had so much compression on a standard engine that it was almost impossible to turn over and with a single head gasket, the air/fuel mix was being squeezed into half the space saturating the sparkplug with fuel, preventing the sparkplug from firing the mixture.
I had to add another two head gaskets for the engine to run and i needed about half throttle just for the engine to idle.
At full throttle the engine had no power, so much so that it couldn't even get me up my driveway in first gear.
returning to the standard cylinder head and a single gasket, all the power returned, just as normal.
Fabian

As I said, no problem with firing, it starts always in 2 kicks - one with full choke to prime, then one kick with no choke and it starts easily.
I have more power all through the rev range than with the standard head.
I agree that it's almost impossible to turn over with the shift kit's standard gearing. I think that for me at 50kg, (110lb), it needs higher gearing from jackshaft to chainrings, then lower gearing from chain rings to rear cluster. That should make starting easier, (for me on a centre-stand), without affecting road speeds while under power.
I'll put more thought into my gearing after a ride or two.

I was concerned about starting, but at least I can start it, but only on the stand. There's no way that I could pedal through one complete revolution of the cranks.

... Steve

 

[Fabian]

With the shift kit and billet head, i tried to pedal start the engine for about 20 meters.

The next thing i knew was the next door neighbour waving over me to see if i needed an ambulance.
I was lying on my back on the nature strip, nearly passed out from the pedal start attempt.

Fabian

 

[210061741]

I just recieved Jims Billet Head Yesterday.

I will figure out what the comp ratio is and let u know.

 

[EnFlaMEd]

God you guys are soft

 

[AussieSteve]

With the shift kit and billet head, i tried to pedal start the engine for about 20 meters.
The next thing i knew was the next door neighbour waving over me to see if i needed an ambulance.
I was lying on my back on the nature strip, nearly passed out from the pedal start attempt.
Fabian

Mate, I can believe it. You did well to get 20 metres. I have emphysema and can't do one turn of the pedals, even on the stand. Lucky it starts easily.

I just recieved Jims Billet Head Yesterday.
I will figure out what the comp ratio is and let u know.

210061741, 'Jim's' billet head? Jim who? I'll be interested to hear, not just compression ratio, but actual compression in psi, out of interest. (I wouldn't know how to calculate compression in psi from compression ratio, unless it's as simple as TDC cylinder pressure divided by ambient air pressure. ie. 142psi / 14psi (at sea level) = 10.14 I don't think it's as simple as that, is it?

66cc?

... Steve

 

[AussieSteve]

God you guys are soft

Easy to say when you're 25 and, I assume, reasonably fit.
Say the same when you're 51 and have emphysema.
Mate, if I was soft, I'd drive a car and not f... around with these things.

... Steve

 

[EnFlaMEd]

Its ok Im just stirring steve hence the

I am aware of your medical condition. That would certainly make things difficult. Probably good reason for me to quit smoking for good.

Mine is a pain to start at times too. I find the best way is to pedal and drop the clutch while still pedaling. Otherwise you can get a bit of a roll happening, let the clutch out and then while off the seat drop down hard on the pedal. I know SBP don't recommend the latter suggestion but I'm still running the original freewheel after nearly 1600kms.

 

[AussieSteve]

Its ok Im just stirring steve hence the
I am aware of your medical condition. That would certainly make things difficult. Probably good reason for me to quit smoking for good.
Mine is a pain to start at times too. I find the best way is to pedal and drop the clutch while still pedaling. Otherwise you can get a bit of a roll happening, let the clutch out and then while off the seat drop down hard on the pedal. I know SBP don't recommend the latter suggestion but I'm still running the original freewheel after nearly 1600kms.

No problems. (Not familiar with the 'razz' smilie)
Smoking doesn't have much going for it, and costs a fortune.
Not that easy to give up, though. I still have a few half-cigarettes a day.

As long as I can keep kick-starting on my stand, I'm fine. (I must get a spare stand soon, though, before I break this one.)
Dropping the clutch while pedalling won't work for me - I can't keep pedalling with the clutch out.
In emergencies, I'll use the 'drop down hard on the pedal' method while rolling, but I'll avoid it due to SBP's suggestion. The sudden take-up of the freewheel could break it.
That isn't an issue on the centre-stand, since the back wheel isn't already spinning. One good push of the RHS pedal...
To make starting easier, I think I need a higher gearing from jackshaft to chainrings, then a lower gearing from chainrings to rear gear cluster, to compensate. I'm considering replacing the 44T/36T combo with 36T/30T.
I'll do the calc for speed in each gear and kick-start ratio with 36/30 later on
and see how it looks on paper.
(Fabian started a thread on this subject a few days ago, I'll have to revisit it.)

... Steve

 

[Fabian]

Personally, i would prefer to use the following gearing combo, as i like to input pedal power - pretend pedaling is actually harder on a long ride and i get calf cramps from doing so.

Jackshaft sprocket - 9 tooth
Chainwheel sprocket that's driven from the Jackshaft - 48 tooth

Chainwheel sprocket driving bicycle chain to the rear cassette - 44 tooth.


This combo slows down the crank chainwheels allowing sensible cadence.
If i could have a custom gearing set, i would run the same 5.33 chainwheel to Jackshaft ratio but using an 11T - 60T.
The increased radius of the 11T Jackshaft sprocket reduces chain angularity and increases chain life.


What is stopping me from changing to the 9T - 48T combination is the significant step up ratio from my current chainwheel gearing, being a 44t - 11T.
I find it very difficult to pedal over the engine with a 44T - 11T so it would be impossible to do so with a 48T - 9T.

I've mentioned this to both Jim at SickBikeParts and Tony at RockSolidEngines.
My solution was a simple one - simply drill and tap the cylinder head to accept a chainsaw style decompression button.
The engine would be easy to pedal start, regardless of what gearing is used.

Fabian

 

[jlebh1]

if anyone needs a different sprocket for there shift kit ive got a, 9 tooth but 2 of the teeth need straitening as they are a little bit bent, if anyone wants it ill sell it for $5 and you pay for the postage, about $5.