Basically not a basic

[mikeyboy]

Last year I acquired this derelict 1979 R100s,
I initially thought it would just be good for a few parts but once I started stripping bits off it I realised that it had done very few miles.
It came from the estate of a deceased hoarder.
I recon it’s only done 1or 2 k miles,
Then crashed and dumped in a shed.
The engine and gearbox are essentially brand new.

 

[mikeyboy]

I’m still gathering parts ,but you get the gist.
R80 basic lookalike with a 100cc heavy flywheel motor.
What’s not to like

 

[Wapping]

That blue is, oddly, one of the things I miss about my HP2 Sport. BMW got it exactly right.

It’ll be interesting to see how the ‘Basic-not-a-Basic’ develops.

 

[Stirlingmoz]

What RAL code did you choose for the frame Mikey ?

I went 5015 sky blue for Money pit but it’s possibly a little light to be a true ‘basic’ copy.

 

[Bubb]

What’s not to like….. well , for me, it’d be the heavy flywheel motor, as I prefer how the later lighter flywheel engines spin up easier.
The rest of the bike will, I’m sure, be a wonderful machine if your previous builds are anything to go by.

Keep on with it, and keep us updated and entertained.

 

[mikeyboy]

What RAL code did you choose for the frame Mikey ?

I went 5015 sky blue for Money pit but it’s possibly a little light to be a true ‘basic’ copy.

I’ll check and come back to you

 

[mikeyboy]

What’s not to like….. well , for me, it’d be the heavy flywheel motor, as I prefer how the later lighter flywheel engines spin up easier.
The rest of the bike will, I’m sure, be a wonderful machine if your previous builds are anything to go by.

Keep on with it, and keep us updated and entertained.

Ha,each to their own.
Light flywheel 100’s are often quite vibey,
As to spinning up faster,I think the reality when the engine is trying to push 200kg of bike and 100 kg of rider it makes little or no difference.
If it did,the light flywheel bikes would fly away on 0 to 60 times,
If you want to test the reality,
Ride my 100s back to back with my 100 cs,
Have you ever ridden light vs heavy back to back?

 

[Bubb]

Mikeyboy
I’d love to take you up on that offer….it might change my mind as I have never done a back-to-back test of heavy v light flywheeled bikes.

I’m sure this “not a basic” will be great when finished, whatever the flywheel…..

Oh, BTW, I’m NOT 100kilos…….!

 

[mikeyboy]

Engine all done,
New valves and piston rings,
Bores honed
New op relief spring,conrod bolts,flywheel bolts,
Stainless pushrod tubes

 

[mikeyboy]

They fit here

 

[Kitsilano]

@mikeyboy LOVE that blue!

 

[mikeyboy]

What’s not to like….. well , for me, it’d be the heavy flywheel motor, as I prefer how the later lighter flywheel engines spin up easier.
The rest of the bike will, I’m sure, be a wonderful machine if your previous builds are anything to go by.

Keep on with it, and keep us updated and entertained.

Bubb,
I’ve been thinking about this.
I’ve often heard it repeated about light flywheel motors “ spinning “ up faster,
Whilst probably true when blipping the throttle ,clutch in etc,
In conversation with SCRIMINGER one day I asked him the difference between light/ heavy,
He just said that light flywheel motors just gave the impression of being quicker.
So to put it in real world context,
An unloaded light flywheel engine will rev more freely/ quicker.
What effect if any will this have on an engine under full load in third gear trying to accelerate up a hill.
I’d say the answer is zero.
What effect would it have on an engine ,if attempting to drag race,
Well, the maximum amount of work the engine has to do is propel the bike from zero velocity to the time to change gear.
The engine isn’t working hard to spin up,it’s working against a huge load,
Hmmm.
A 1000 cc boxer motor fires once every revolution,bang, bang.
Light/heavy same crank,same rods same pistons,same heads valves and carbs.
Once under load,same max power, same ish torque.
Heavy flywheel,
Nice stable idle,better low down torque,less vibration,smoother power as heavy flywheel damps out power pulses.

 

[Bubb]

Bubb,
I’ve been thinking about this.
I’ve often heard it repeated about light flywheel motors “ spinning “ up faster,
Whilst probably true when blipping the throttle ,clutch in etc,
In conversation with SCRIMINGER one day I asked him the difference between light/ heavy,
He just said that light flywheel motors just gave the impression of being quicker.
So to put it in real world context,
An unloaded light flywheel engine will rev more freely/ quicker.
What effect if any will this have on an engine under full load in third gear trying to accelerate up a hill.
I’d say the answer is zero.
What effect would it have on an engine ,if attempting to drag race,
Well, the maximum amount of work the engine has to do is propel the bike from zero velocity to the time to change gear.
The engine isn’t working hard to spin up,it’s working against a huge load,
Hmmm.
A 1000 cc boxer motor fires once every revolution,bang, bang.
Light/heavy same crank,same rods same pistons,same heads valves and carbs.
Once under load,same max power, same ish torque.
Heavy flywheel,
Nice stable idle,better low down torque,less vibration,smoother power as heavy flywheel damps out power pulses.

I will have to arrange to come up and try light v heavy…..
I see what you’re getting at, and maybe I’m biased as I’ve only had one heavy flywheel bike ( 90/6) ….

Thanks mate, and keep the build details comming

 

[timeandtide]

Interesting discussion, personally I’d be very unlikely to disagree with Mikeyboy!

 

[mikeyboy]

Interesting discussion, personally I’d be very unlikely to disagree with Mikeyboy!

Hi Richard,
It’s not really my view,
Rob farmer said much the same years ago,
Scrimmy said the same years ago.
Charlie has stripped at least two light flywheel motors recently to have the crank,rods etc balanced due to REALLY excessive vibration,
Another customer declined to spend.
There are more than a few light flywheel motors out there that are very badly balanced.
It’s a very well acknowledged fact that 80 motors are smoother.
I’ll elaborate if required

 

[Mad Hatter]

Mikey, would my R60/6 have had the heavy flywheel? I don't know if it was that or the smaller cc with less vibes but that bike was like a sowing machine with a lovely mellow engine character but deceptively rapid. If that's the heavy flywheel effect I like it

 

[Stirlingmoz]

In my experience the heavy flywheel bikes have a much heavier pull at the handlebar clutch lever.

My light flywheel bikes have a much lighter pull at the bars.

Makes for less hand strain when going into London as there is lots of clutch work.

Likely the result of different clutch springs rather than the flywheel itself but the difference is marked.

 

[casbar]

In my experience the heavy flywheel bikes have a much heavier pull at the handlebar clutch lever.

My light flywheel bikes have a much lighter pull at the bars.

Makes for less hand strain when going into London as there is lots of clutch work.

Likely the result of different clutch springs rather than the flywheel itself but the difference is marked.

Having had quite a few R80s previously and ridden a few heavy flywheel R100s. My R100CS which is an 82, so a light flywheel, is defiantly the smoothest 100 I have ridden. No vibration and great pickup.

The bike had a complete rebuild in 2016 and has covered 5k miles since, (Ive only had it just over 2 years). It was restored by Keith Shaw, who built it for himself, so I would say the skill of the engine builder has a lot to do with it.

 

[bakerlonglegs]

Oh yippee! I’ve just spent a fortune getting the shittest airhead engine refurbed, an R100 light flywheel motor. There is no end to my fuckwittery…

 

[Bubb]

Oh yippee! I’ve just spent a fortune getting the shittest airhead engine refurbed, an R100 light flywheel motor. There is no end to my fuckwittery…

Surely the “shittiest” was the r45??
I’m sure your engine, and the rest of the bike surrounding it will be fine…