EnFlaMEd
Member
Thats my driveway which I cruise up at the start of the video. I think it would be impossible to motor up without the shift kit.
How much compression do you have with standard head and RockSolidEngines Billet Head
- Thread starter Fabian
- Start date
Thats my driveway which I cruise up at the start of the video. I think it would be impossible to motor up without the shift kit.
2
210061741
Guest
not if you had a PK80-J
AussieSteve
Active Member
That's an exaggeration. That's one steep driveway. Without a run-up, a PK80 w/ 26" wheel and 44T sprocket couldn't do that without gears. I don't think the pics do justice to the steepness.
Stock compression: ~6-6.5:1
Slant: 8.5:1
This is the only real difference between these engines. That won't increase bottom-end that much.
EnFlaMEd's pics don't do justice to how steep that hill is. Even a 66cc with the billet head at a corrected 9.5:1 compression with good fuel/air mix, 44T sprocket and 50kg load couldn't do that without a run-up.
(Post a video proving me wrong.)
... Steve
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Fabian
Well-Known Member
If a single speed setup can push a motorised bicycle up a seriously steep driveway without one heck of a run-up, i'll be beating a path to the engine manufacturers door; throwing my SBP shift kit in the bin and returning to basics!
EnFlaMEd
Member
The pictures don't do it justice really. Even some cars struggles to get up, especially if they are carby fed and haven't been warmed up. Otherwise traction is the biggest issue. Many a car has had to be towed out after dropping a wheel off the side in winter. My Toyota tries to leave black marks the entire way up if I am reversing.
AussieSteve
Active Member
EnFlaMEd, I forgot to mention, although you're probably already aware, your engine is 4-stroking in the low to mid throttle openings. Just watched your video again.
Like mine, it's too rich except at WOT. What size main jet are you using and where is your slide needle set? (If your needle is not at it's lowest setting already, dropping it down a notch would help to lean out your mid-throttle mixture.)
I noted that you aren't revving out very high, about 4-5000 max, and get to 62kph. Does it wind out much more if you hold WOT in top gear for a while? (Mine hits ~7400RPM.)
Just wondering about top speed.
I'm seriously considering buying a SBP shift/jackshaft kit, then see if I'm still capable of pedal-starting.
Otherwise, I'm thinking of buying a shift kit, then working out a way to modify it such that the drive freewheel can be locked for starting then unlocked when the engine fires. Not sure how. Any ideas, anyone? Maybe some sort of DIY dog-clutch, cable-operated by a lever? Pull in the lever to lock the freewheel, release it to unlock.
Anyone that can come up with a simple solution could sell a lot of these things. (To me first, please.)
That way, the bike could be pedalled up to speed, then the freewheel could be locked for a moment allowing momentum to start the engine. As soon as it fires, release the lever and the sprocket freewheels again. (Much like a second clutch or the central locking differential on some four-wheel-drives.)
... Steve
Like mine, it's too rich except at WOT. What size main jet are you using and where is your slide needle set? (If your needle is not at it's lowest setting already, dropping it down a notch would help to lean out your mid-throttle mixture.)
I noted that you aren't revving out very high, about 4-5000 max, and get to 62kph. Does it wind out much more if you hold WOT in top gear for a while? (Mine hits ~7400RPM.)
Just wondering about top speed.
I'm seriously considering buying a SBP shift/jackshaft kit, then see if I'm still capable of pedal-starting.
Otherwise, I'm thinking of buying a shift kit, then working out a way to modify it such that the drive freewheel can be locked for starting then unlocked when the engine fires. Not sure how. Any ideas, anyone? Maybe some sort of DIY dog-clutch, cable-operated by a lever? Pull in the lever to lock the freewheel, release it to unlock.
Anyone that can come up with a simple solution could sell a lot of these things. (To me first, please.)
That way, the bike could be pedalled up to speed, then the freewheel could be locked for a moment allowing momentum to start the engine. As soon as it fires, release the lever and the sprocket freewheels again. (Much like a second clutch or the central locking differential on some four-wheel-drives.)
... Steve
EnFlaMEd
Member
Yeah she does 4 stroke a bit but I am running a 1.6mm main jet believe it or not. Currently the needle is set in the middle slot as the last time I tried to lean it out a bit more she didn't like it so I put it back however I have since discovered that my spark plug was quite loose and possibly causing an air leak.
I have had a few people say that I'm being pretty soft with the revs. This is only because I don't know what limit I can rev it to. Do you think I can safely give it a bit more curry without damaging anything? I have never revved it right the way out in 9th gear before but have done over 70kmh on a slight decline in that gear. I think my best on the flat is about 66kmh but even then I had to back off as I was passing traffic and it was a bit dodgey.
Pedal starting isn't too bad once you get the hang of it. You can actually pedal while seated and then drop the clutch as one of your legs is just about to make the power stroke and then continue pedalling until it starts. Otherwise you can jump on it a bit while standing. I know SBP don't recommend that but I haven't broken anything on mine yet and I have done about 1400km.
I have had a few people say that I'm being pretty soft with the revs. This is only because I don't know what limit I can rev it to. Do you think I can safely give it a bit more curry without damaging anything? I have never revved it right the way out in 9th gear before but have done over 70kmh on a slight decline in that gear. I think my best on the flat is about 66kmh but even then I had to back off as I was passing traffic and it was a bit dodgey.
Pedal starting isn't too bad once you get the hang of it. You can actually pedal while seated and then drop the clutch as one of your legs is just about to make the power stroke and then continue pedalling until it starts. Otherwise you can jump on it a bit while standing. I know SBP don't recommend that but I haven't broken anything on mine yet and I have done about 1400km.
AussieSteve
Active Member
I'd forgotten about the 1.6mm main jet. The size still amazes me. Goes to show just how much difference there is between engines. Mine runs best on an 0.72mm jet, with the slide needle at it's lowest setting.
Yeah, I reckon you could easily wind it out a fair bit more, probably another 1000RPM, but with the gears that's not necessary. For me, the whole point of gears is to keep engine revs down a bit. I don't want to do more than about 50kph, most of the time, except on the open roads where traffic is travelling fast.
After seeing yours, I want a shift kit, so I'll probably buy one soon and see how I go.
This is what worries me, though. I'm 51, 50kg and have emphysema, so I think it'll be touch and go:-
... Steve
2
210061741
Guest
Prolly you are right if you try from a dead stop.
But i think if i was goin 10 or 15 mph i could make it easy.
But like you said u cant really see how steep it is.
But i think if i was goin 10 or 15 mph i could make it easy.
But like you said u cant really see how steep it is.
AussieSteve
Active Member
Finally got a ride on mine today to test the changes - billet head, DIY 'O' ring on inlet tube, SBP air filter, went from 16:1 fuel oil to 20:1, (even new rear-view mirror, double centre-stand and 3L tank) and a new stock NT carb.
Wow, a different bike. I need a few days to re-tune, but heaps of power, easy to start and I was pleased to see, my mid-throttle openings are back within tuning range. Even easy to pop monos from about 3000RPM, or popping the clutch at about walking speed.
Now, with the needle at it's lowest where it was, mid-range is lean and running a bit hot.
The surprise is that WOT is now rich and 4-stroking, even with my 0.72mm main jet.
It goes like ???? at mid-throttle and easily hits 50kph, but bogs at WOT, enough to actually slow down. Might have to go to 0.7mm or even smaller.
The best part of today was discovering that I can easily kick-start on my new centre-stand, even with a run-in engine and billet head. More here.
Also, the 'Mountain Mirrycle' mirrors are good on MBs - a little bit of vibration but I could see well. (Daytime only, so far.)
I was busy playing with kick-starting today, but tomorrow I'll do a compression test and start re-tuning the carb.
I'll post results.
Meantime, just ordered a HD shift kit. Can't wait.
... Steve
Wow, a different bike. I need a few days to re-tune, but heaps of power, easy to start and I was pleased to see, my mid-throttle openings are back within tuning range. Even easy to pop monos from about 3000RPM, or popping the clutch at about walking speed.
Now, with the needle at it's lowest where it was, mid-range is lean and running a bit hot.
The surprise is that WOT is now rich and 4-stroking, even with my 0.72mm main jet.
It goes like ???? at mid-throttle and easily hits 50kph, but bogs at WOT, enough to actually slow down. Might have to go to 0.7mm or even smaller.
The best part of today was discovering that I can easily kick-start on my new centre-stand, even with a run-in engine and billet head. More here.
Also, the 'Mountain Mirrycle' mirrors are good on MBs - a little bit of vibration but I could see well. (Daytime only, so far.)
I was busy playing with kick-starting today, but tomorrow I'll do a compression test and start re-tuning the carb.
I'll post results.
Meantime, just ordered a HD shift kit. Can't wait.
... Steve
Last edited:
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