102 gearbox ratios

rosbullterier · Post by **rosbullterier** » Sun Jan 04, 2009 9:13 pm

Charles, you state to John1952 in his query regarding propeller evolution:

'Late forties early fifties there was a bit of experimentation, and higher power/slower revving motors ended up with more blades of a larger clover-leaf shape.'

Does this mean the 102 boxes, apart from the Plus, do have different ratios? If so can they be externally distinguished?

I was counting on them all being 12:30!

Horsley-Anarak · Post by **Horsley-Anarak** » Sun Jan 04, 2009 11:12 pm

There you have it, your prop was not turning fast enough because of the wrong gearbox

H-A

rosbullterier · Post by **rosbullterier** » Mon Jan 05, 2009 12:15 am

Allan you'd better be turbo charged plus Nitrous for next year.
I know what you look like now . . .

Post by **charlesp** » Mon Jan 05, 2009 1:16 am

No. What I meant was the experimentation was with props. The gearboxes are (basically) the small and sleek or the ones like a turnip.

I regret that you're back to nitrous oxide in your search for greater power. Either that or the other Charles will come in here and tell you exactly which block (big porting differences) mated with which gearbox and which prop will give you the best power output for your craft.

B.S. did give this a bit of thought, and they never turned this into a production model.

Come on Charles, share a bit of the mother lode of Seagull tuning lore...

rosbullterier · Post by **rosbullterier** » Mon Jan 05, 2009 4:03 pm

Charles, Seagull and Nitrous Oxide - the word oxymoron springs to mind!

It was a joke Charles, just a josh at HA . . .

Andy

Horsley-Anarak · Post by **Horsley-Anarak** » Mon Jan 05, 2009 6:38 pm

I was not going down the Nitrous route, I was thinking more of a belt driven supergharger. Simple just add another pulley above flywheel, easy peasy. Now all I need is a nice cheap blower about the size of a coke can.

H-A

Post by **Charles uk** » Mon Jan 05, 2009 7:29 pm

I've been called a Moron before, but never an oxymoron do I have to get an O2 mobile phone?

Sorry your not going to get big porting diffences with 102 cylinders, only minor ones.

So here's your shopping list,

SD cylinder with cleaned & gas flowed ports, clean water jacket & 5/8" reach spark plug.

SD crankcase with new main bearings, reconditioned needle roller crankshaft with new pin & new big & little end bearings, Crankcase internal volume to be reduced, to suit crankshaft & increase crankcase compression.

Depending on how well you've gas flowed the inlet port, a new Amal 416 or 418 carb & a selection of suitable main jets.

Now the bottom end.

Model 75 water pump housing & a century water delivery pipe ( to be cut & fitted later) featherweight gear box with a modified propshaft to accept Yamaha or Mariner 3 bladed 4hp shearpin prop.

Come back to me when you've collected all the above & I'll talk you through assembly & the ignition permutations.

timberman2004 · Post by **timberman2004** » Mon Jan 05, 2009 9:51 pm

good ...right ....OK...got it ...just get my anorak ...

<<whew>>.... these speed boys just can't help themselves

Horsley-Anarak · Post by **Horsley-Anarak** » Mon Jan 05, 2009 10:08 pm

I find that the ones with a fold away hood, and both zip and Velcro are best. But don't forget that they best made from Gortex fabric and need to have a draw string aroung the waist.

H-A

P.S. Have not told H.I.D. that I have a new Ebay shopping list for the super fast Seagull project, at least it will make a change from searching for "mens lightweight waterproof coats"

rosbullterier · Post by **rosbullterier** » Mon Jan 05, 2009 11:29 pm

Talking about race tuning - putting the 170 back together after its sonic vibration deep clean - I found the Amal 420 needle has three holding slots.
Well, this is an option too far, more than I can contend with. It seemed to work perfectly well using 25:1 mix on the bottom slot with plug the right colour.

Do I experiment on a weaker mix by dropping the needle a slot?

Hugz · Post by **Hugz** » Mon Jan 05, 2009 11:35 pm

H.I.D. Her In Distress????

Post by **Charles uk** » Mon Jan 05, 2009 11:35 pm

If the plug is the right colour, it ain't broke so don't fix it.

rosbullterier · Post by **rosbullterier** » Tue Jan 06, 2009 12:52 am

That's not the point - what are the other needle slots for?

Post by **Charles uk** » Tue Jan 06, 2009 1:19 am

The carb was made by Amal for any 2 stroke motor manufacturer who required a 20mm carb for their application, depending on their needs & performance requirements.

The 420 as fitted by Seagull to the 170 or the 160 inboard was fitted with a 140 main jet, which enabled the owner to fine tune their mixture without going to the expense of ordering a larger or smaller main jet, whilst in use.

Can I have a red anorack without a hood, Gortex would be nice too!

rosbullterier · Post by **rosbullterier** » Tue Jan 06, 2009 1:29 am

thank you Charles, now go to bed . . .