4 stroke jack shaft with 7 speed cassette

Sorry I just dont understand....why do I want to pedal with a running engine???

Why _wouldn't_ you? Chevrolegs make more torque than any of these small engines. Direct-mounted clutches aren't the smoothest at low speed with that engine class, either.

The 2-stroke engines have a ~3.26:1 (I don't recall the exact number)

20T -> 82T for a reduction of 4.1:1 :rolleyes:

You 2 Einsteins will co-operate and get along, nuff said!

Probably aint gonna happen. I don't suffer fools very well; it's a nasty character flaw, I know.

I dont get it.................

I'm not getting it, either. :whistle:
 
I thought I posted this earlier but evidently I did some thing wrong?????
Anyhow Its been a while since I have posted ..probably 2013 when I built my 2 stroke.
View attachment 59303

I now want to upgrade to a 79cc Predator with a jack shaft running a 7 speed cassette.
I have found very little info on what if any transmission to use for this setup.

I have a 35t sprocket that I'm thinking of running on the left side off a 10t clutch.
Anyone have any comments concerning this approach or am I going in the wrong direction????

Just getting started so I'm open to suggestions.
Good to be working on my bike again.
Thanks in advance for any assist, Ron
some progress

Hi all.....
I did receive a response concerning my use of the following gear set, but not from here.
It appears I need to find an additional 3:1 somewhere in the drive line??
I'm still going ahead with the 35t sprocket for now, here is what I'm using:
@ 6000 rpm with 10t clutch to a 35t sprocket on the left jack shaft (SBP 4 stroke kit), and
a 10t sprocket on the right jack shaft to a 48t at the crank mated to a 30t that runs to a 7 speed cassette.
with 12,14,16,18,21,26,32 tooth sprockets would it produce the following?? (ball park)

12t 9.57:1 @ 48.46 mph
14t 11.4:1 @ 40.62 mph
16t 13.6:1 @ 34.10 mph
18t 16.8:1 @ 27.62 mph
21t 20.8:1 @ 22.28 mph
26t 24.8:1 @ 18.76 mph
32t 29.2:1 @ 15.88 mph 1st gear
I really don't know if this will work but it seems as though it should......that was my question.
Is this approach reasonable enough to accelerate from a standing start in 1st gear with out choking down, and allow advancing thru the gears to a sustainable 25+ mph.
Just asking for opinions, if I'm all wet that's OK, I just don't wish to spend $150-$300 on a gear reduction 'transmission' when I have a gear that may(might) do the trick

I tore down the bike and have completed painting a have the initial re-assemby done.
Have parts coming in ....
Had to use steel wool on the handle bar and goose neck to clean them up.
Put on the dual brake lever and front brake disk 160mm.
I slipped on a new twist shifter and determined that the throttle and kill switch when installed will prevent it's use, so I'm getting the thumb shifter, hope it works better.
Have new rims, strips, and tubes, rims are Sta Tru with disk brake hubs on both, and a new 7 speed cassette.
Here are a couple of pictures....View attachment 59364
View attachment 59365
View attachment 5936659367[/ATTACH]View attachment 59368

Why _wouldn't_ you? Chevrolegs make more torque than any of these small engines. Direct-mounted clutches aren't the smoothest at low speed with that engine class, either.



20T -> 82T for a reduction of 4.1:1 :rolleyes:



Probably aint gonna happen. I don't suffer fools very well; it's a nasty character flaw, I know.



I'm not getting it, either. :whistle:
 
Well I ran the bike set up with (10->35 / 10->48 / 30-> 32......12 cassette)
Take off was strong and top end good @35mph, but I separated the derailleur chain to many times.
So I reconsidered the shifting approach and decide to revert back to the way my 2 stroke was set up with 44T rear sprocket. I'll set aside the gearing for now, and revisit it in the future, always nice have to have an upgrade in the wings.:)
The 2 stroke was 20->82 .... 11->44 with FDR @16.40:1
The 4 stroke is 10->35 .... 9->44 with FDR @ 17.11:1
This puts me as close to the 2 stroke FDR as I can get with the 35t sprocket, I'm off .71

I installed a 44T sprocket with the 6 bolt mount to the rear disk brake hub, an used the 9T that came with the SBP 4 stroke kit.

I modified (and poorly I might add) the SBP motor mount to accept the HF engine, and all's well so far.
After my first test run with the clutch 10t to 35t on the SBP jack shaft, and 9t off the jack shaft to 44t @ the rear wheel.
Take off is strong, bike wants to go, you can feel it.
nice 13-14 mph @ 2800->3000 rpm
29-30.4 mph as read from cateye Velo 7 at wot 6250-6500 rpm
This is good enough for me right now.

I still dont comprehend the need for 'transmissions' to build a 4 stroke????
The SBP jack shaft is simple, changeable, and relatively inexpensive, least thats the way I see it.
I added 2 chain tensioners to the left side to hopefully reduce adjustment while testing.
Yes I'm going to run a 10mm self taper in the rear tensioner.
Finalized my exhaust system, I think.
Pictures included, thanks for looking, comments good or bad appreciated.
Ron
OH...MERRY CHRISTMAS everybody:p
 

Attachments

  • DSC00118.JPG
    DSC00118.JPG
    192.2 KB · Views: 335
  • DSC00119.JPG
    DSC00119.JPG
    225.9 KB · Views: 378
  • DSC00120.JPG
    DSC00120.JPG
    199.1 KB · Views: 367
  • DSC00123.JPG
    DSC00123.JPG
    228.5 KB · Views: 327
  • DSC00124.JPG
    DSC00124.JPG
    215.2 KB · Views: 359
  • DSC00125.JPG
    DSC00125.JPG
    224.2 KB · Views: 337
  • DSC00126.JPG
    DSC00126.JPG
    164.9 KB · Views: 368
  • DSC00127.JPG
    DSC00127.JPG
    214.5 KB · Views: 361
  • DSC00128.JPG
    DSC00128.JPG
    188.7 KB · Views: 399
  • DSC00129.JPG
    DSC00129.JPG
    191.5 KB · Views: 368
Well I ran the bike set up with (10->35 / 10->48 / 30-> 32......12 cassette)
Take off was strong and top end good @35mph, but I separated the derailleur chain to many times.

I reconsidered the shifting approach and decide to revert back to the way my 2 stroke

I still dont comprehend the need for 'transmissions' to build a 4 stroke????
The SBP jack shaft is simple, changeable, and relatively inexpensive, least thats the way I see it.
A 2-stoke engine has a built in gear reduction and clutch.
A 4-stroke has neither, so it has to be external.
I call them a 'transfer case', it has the clutch and a simple gear reduction but has no shifting gears.

Sure, you can do that with a jackshaft to use your bikes gears to do a shifting gear range, it just has to be one hell of a reduction without an initial transfer case reduction to start from like a 2-stoke has to start with is all.
 
Back
Top