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

[AussieSteve]

So, I was thinking of going to 11T/36T, but you say you have trouble pedalling over the engine, with a ratio of 3.2:1?
I was considering that combo myself.
How did you go with the stock 10T/44T, at 4.4:1?
That's what I'm having trouble with.

5.33:1 would be way too hard to pedal-start.

I've been doing a heap of calculations for the different combos available from SBP, speed in each gear and pedal(kick)-start ratios.
When I'm finished, I'll post results in a new thread.

... Steve

 

[Fabian]

Exactly Steve,

Standard engines seem to have 115 PSI compression and with an 11T-44T (4.0 : 1) it's difficult to pedal start.

I've haven't tried a 10T - 44 (4.4 : 1) as the 11T - 44T is hard enough as it is, and never even bothered to experiment with a 9T - 48T (5.33 : 1) combo as i know the engine simply could not be pedal started, and that's with standard compression.

If fitted with a billet cylinder head (145 PSI compression) the 11T - 44T combo would be almost impossible to pedal start.

The only solution is to fit a decompression button in the cylinder head.
I can't see why it would be a problem to drill and tap a 6mm hole and thread in a decomp.

Maybe i'll have to get to a small engines shop and have one pulled out of a damaged chainsaw, fitting the thing to my engines cylinder head as an experiment.

Fabian

 

[Hajuu]

jesus christ. You do realise these are meant to be FUN right?

If you want a freaking motorbike, buy a motorbike. In the hundreds of hours you've probably wasted trying to get a bit more power out of it, you could have worked and bought a higher class of vehicle.

Pushing boulders uphill will get you nowhere.

 

[AussieSteve]

jesus christ. You do realise these are meant to be FUN right?

If you want a freaking motorbike, buy a motorbike. In the hundreds of hours you've probably wasted trying to get a bit more power out of it, you could have worked and bought a higher class of vehicle.

Pushing boulders uphill will get you nowhere.

You just don't understand. It's the hobby - the fun of building and getting things just right.
Once you get over your initial enthusiasm, you'll realise how limited these things are, with one gear and no power.
Meantime, you've got to get yours to run reliably and stop losing the bucking-bar, before you criticise, I think.

... Steve

 

[AussieSteve]

Exactly Steve,

Standard engines seem to have 115 PSI compression and with an 11T-44T (4.0 : 1) it's difficult to pedal start.

I've haven't tried a 10T - 44 (4.4 : 1) as the 11T - 44T is hard enough as it is, and never even bothered to experiment with a 9T - 48T (5.33 : 1) combo as i know the engine simply could not be pedal started, and that's with standard compression.

If fitted with a billet cylinder head (145 PSI compression) the 11T - 44T combo would be almost impossible to pedal start.

The only solution is to fit a decompression button in the cylinder head.
I can't see why it would be a problem to drill and tap a 6mm hole and thread in a decomp.

Maybe i'll have to get to a small engines shop and have one pulled out of a damaged chainsaw, fitting the thing to my engines cylinder head as an experiment.

Fabian

Now, where was I?
The other option to a decompressor is to get the pedal-starting gearing just right, then select the second chainring for drive gearing. Hard to get it just right with the range of sprockets available - 1-tooth increments would be great.
The problem with this method is that the chainring RPM can be a fair bit higher than stock.
ie:-
With stock 10T/44T jackshaft>chainring gearing, the chainrings do 241RPM, (4 revs per second), at 7400RPM.

With 11T/36T, the chainrings do 325RPM, (5.4 revs per second), at 7400RPM.

I guess this could wear out the freewheel bearing prematurely, but probably wouldn't be a problem otherwise.

The other inherent problem, (with my bike), is the gear spread of the rear cluster. Wider-spaced ratios would be better.
Mine are: 28,24,21,18,16,14

I've got plenty of figures for the new thread, so I'll get it started soon.
I've pretty well figured out what I want.

With the above cluster and based on a max RPM of 7400, I have speed in each gear, ratio and pedal-start ratios for:-
10T>44T/36T, (stock with shift kit)
10T>36T/30T
10T>30T/24T
11T>36T/36T
11T>36T/30T
11T>36T/24T

... Steve

 

[Hajuu]

I get it, and I've enjoyed my time building and maintaining my ride so far, I wouldn't however waste 10 pages on a forum trying in vain to boost my power output marginally.

THAT, I don't understand.

 

[AussieSteve]

I wouldn't however waste 10 pages on a forum trying in vain to boost my power output marginally.
THAT, I don't understand.

'waste 10 pages' What do you think the forum is here for?
'trying in vain' So, you're saying that these mods, (ie billet head), don't succeed in boosting power?
If you don't understand, don't like the thread and can't contribute to it, then don't read it and don't post in it.
Some of us do understand, like the thread and can contribute.

... Steve

 

[AussieSteve]

I started the new thread on ratios, speeds etc in 'Frame-Mounted Drive Trains', SBP Shift Kit - Ratios, Speeds and Pedal-starting.

... Steve

 

[Fabian]

Hi Hajuu

All of us have a different focus when it comes to these motorised pushbike engines and kits.

For some it's just the most basic form of transport, like the Volkswagen automobile.
For others it's the pursuit of a hobby in improving the reliability, performance and in some cases, the technology associated with these kits.

In my case, it stems from previous motorcycle racing experience.
A light weight machine and nimble handling chassis is all one can ask for in an uncontrolled category, but this doesn't exist as there would be no parity between machines.
The closest one can get to a motorised bicycle in a full sized machine is a GP 125 bike.
Yes it has way more power but the philosophy of handling over outright power shines through in this category.

In so saying, a motorised bicycle shines through in it's light weight and nimble handling and in this case it's not about the lack of power as they are still pushbikes in essence.

It's not an argument about the merits of motorcycle vs a motorised bicycle or cost outlay compared to a motorbike.

It's all about what you enjoy and how enjoyable the experience may be in the eyes of the person spending time with these motored contraptions.

Fabian

 

[arceeguy]

jesus christ. You do realise these are meant to be FUN right?

If you want a freaking motorbike, buy a motorbike. In the hundreds of hours you've probably wasted trying to get a bit more power out of it, you could have worked and bought a higher class of vehicle.

Pushing boulders uphill will get you nowhere.

I totally agree, but if someone wants to waste their time, who am I to tell them they can't.

I love reading the turbocharger/supercharger threads in the performance forum. Talk about pizzing in the wind! (but highly entertaining)