Modified 102

[headdownarseup]

Here we are talking about modifying an old round block 102 seagull to see if we can generate a bit more power and speed without the motor self destructing itself to bits at wide open throttle, as in a racing situation

You join us now having previously been on "Boats and Seagulls" thread and not quite in the right section of SOS.


Bruce, perhaps you could elaborate on your idea with reed valves. Do you have any pictures that might help explain how this could be done.


Nudge, i know you are a bit of a metal pourer on the quiet. I admire that. If this project were ever to be undertaken by an enthusiast in their shed or garage at home, leaving bespoke casting aside for the moment, i feel that the average joe working on their gull will probably have a limited set of hand tools with which to work and casting something for a specific task to most seems quite a scary thing to do. So with that in mind perhaps we could come back to the idea a bit later once we've gathered some sound ideas before we move to another level.
I would like to know though if you've ever recorded any data from your own 102/boat set up that maybe i could use as a ballpark comparison with some of my own 102's. Engine revs and speed etc. for working out a bespoke "tune pipe" will help me quite a bit, but as i only have my own 102's to work from and a big heavy boat which doesn't really compare that well with what we're discussing here i would like a wider spread of numbers from which i can compare.

For simplicity's sake here, i think many folks would be keen to discover just how far we can safely push the bone stock components that are already inside a typical 102 gull, sensibly upgrade a few bits and see what happens. If needs be, as we get further into this and there just happens to be someone with a 102 and a suitable boat handy maybe we could put some of these ideas into practice and carry out some gentle testing on the water.

Again for simplicity's sake and without using any expensive high tech equipment like dyno's etc. if we try to keep things at a grass root level as far as measuring devices go e.g a cheap tacho for measuring engine speed, for measuring speed through the water i think most of us have a good mobile phone these days with an app that has a gps device built in. They seem relatively accurate to me and readily available to most. Maybe some ideas about a basic set of tools would be good and spanner sizes to those might still be confused with it, particularly some of the newbies that might be interested.

Mr. Naughtybits (is it Jason, i can't remember?)
I'm not at all clued up with the later QB models, but i do understand that they are different internally to a stock 102, so perhaps you could expand on this as well so that we're all aware of what the development actually lead to in these later seagull models.

If we can pool all our ideas into one place, the next logical step would be someone to actually build/modify the stock parts and go testing.


I've already mentioned i'm looking into "tune pipes" so i don't mind building a bespoke expansion pipe for testing purposes if everybody else doesn't mind that is.



Jon

[GarethJ]

I just read the interesting thread this post stemmed from. I would say that in my limited experience of welding stuff, filling the head might be achieved by "cold" arc welding with nickel rods. Time consuming but you eliminate the risk of warping. You'd need to protect the cylinder sides though.

[NaughtyBits]

Jon, my understanding is that as Seagull adopted the more powerful QB design, they found the old crank design (the conrod, in particular) was not strong enough.

Cue BS introducing beefer ali conrods for the QB series, then steel conrods & roller bearing cranks, etc.

[Collector Inspector]

Not reed "Valves" just one is all that is required.

I had this idea a while ago in one of my posts regarding a silver century power head toy..........

An idea from a C-Powa.

You will see in both of these pics how the read block looks and where it fits.

On BS the only place to cut something like this in is top case/under ignition plate/to the side. In other words the reed is horizontal with 90deg to carb.

Obviously one does not need a full standard ignition base.......just the bit on which that points live. Throw the rest away as you will end up using a small remote battery and a modern coil.........really. Chop up a Wipac plate!

The carb size should be kept the same bore as BS.

I have lost my measurement notes/jottings but you might get the idea.

ONE round petal. Because of the size constraints round will seal better than any other shape.

A trendy wedge shape block will defeat the ability of the crankcase suck and blow.

The idea is to NOT INCREASE the crankcase volume.........keep it small and simple. Hmmmm, do some googling for chainsaw or small engine reed asys. I did that but nothing really jumped out at the time.

I will try and find my paper pattern for chopping a top case hole...............

I may revisit as I now have a modeller mate with some outstanding 3D printing hardware.

Comments as to cranks, rods and main bearings should be taken as gospel.

You will adjust your vision slightly to further your goals in a timely fashion.

BnC[/color][/b]

[headdownarseup]

Hmm. nearly the same idea i was thinking, but not quite what i had in mind. Interesting though

I was thinking of fabricating a small "thing" (that's what i'm calling it for now) that's actually fixed into the inlet tract of the 102, similar to your pics with just 1 petal for simplicity's sake. The trouble with my proposed version is that all of the work is going to be done from inside the cylinder as opposed to anything exterior. The cylinders i can lay my hands on at the moment all seem to have varying amounts of space to achieve this proposed idea. The inlet port/stub for these cylinders starts off being round at the carb side, but towards the end of the port (close to the cylinder bore) it transitions into an oblong or oval shape depending on specific cylinder variations and designs, and to me this could make an ideal position for a rudimentary "reed valve" of sorts. The actual physical size of the reed will be quite small however so i'm not too sure how this will affect air/fuel flow or volume that can be drawn into the crankcase before the reed closes.Provided the back side of this proposed reed doesn't encroach into the path of the piston skirt we might have something to work with. It's also possible that for this reed to work there might be some grinding with a dremel tool involved to reach the desired shape so that this reed valve could fit with adequate clearance, but at the same time keeping an eye on port timing as well. Looking at a very knackered block i have that's in bits (literally) i can see there's enough material around the base of the carb inlet to hopefully allow a good enough fixing to hold everything in place.Fixing it securely so it doesn't move will be another big problem as there's not much space to work and any drilling for a screw or small bolt to hold the reed in place will have to be done with a small right angled drill or similar. Provided there's a good flat surface for the reed cage to be fixed onto, any sealing issues could be attended to afterwards. Quite tricky but doable i think. Everything on the exterior of the cylinder being as BS intended, so no issues with fitting carbs etc. (stealthy)

The other idea i have, and keeping the same diameter carb/inlet size etc. is to have a length of pipe approx 1.5 inches long, thick enough in the wall thickness to allow a rebate to be machined to fit onto the stock inlet and accept the carb at the other end. Inside the pipe would be a fabricated reed block (not necessarily as a wedge as in more common types) but similar again to your pics. The trouble here is that the length of the inlet path or tract will have been lengthened a bit which might upset the total volume inside the crankcase before the reed is closed. Stuff the cases a bit to compensate perhaps?

Difficult to show you unless a paper drawing would help explain it better.


Keep these ideas coming guys Good stuff all of this

Jon

[headdownarseup]

Jason

Do you have any pics of these aluminium con-rods at all? I have a few century/102 con-rods of varying types and ages.
How beefy are they?
Could we compare a beefy one with a "normal" one side by side for careful analysis.



I hadn't realised it was you that made these "hot rod" cranks with full circle webbs. Nice job

[NaughtyBits]

I don’t, sorry - working on different motors at the moment. The #4 was in the Kingfisher, before they moved to the needle rollers, I think.

For the mods you’re suggesting, I wouldn’t use any of the traditional BS cranks with ali conrods, personally.

I was just selling the needle roller replacement cranks for a mate. So far, so good with them.

[GarethJ]

You might struggle to find a lot of space to take up with "stuffers" to compensate for any case volume enlargements. Most of the area that looks like space is needed to clear the clunky big end shell bolts. Using up almost all of this space on my "97" brought primary compression to where I thought it ought to be.

[headdownarseup]

I'm not suggesting we go mad with a 102, merely give it a good seeing to, somewhat in a sensible manner.
But it would be kind of fun to see what is possible with some fairly stock(ish) components. Cherry picked of course.

Others may have a different reason for modifying their gull.

Mine are purely for something to go just a little bit quicker than your average sunday afternoon canal chugger, but still look good like all 102's do after all this time I'm certainly not a racer, not any more at least. But i still like speed

[NaughtyBits]

Well - that's me lost.

You went from writing a novella on wanting to fill combustion chambers, making hidden expansion pipes, installing reed blocks, etc., to now not wanting to 'go mad' & only looking 'to go a little bit quicker', after some advice starts coming in. None of the modifications you expressed initial interest in doing are necessary to get your 102 just going a little faster.

I'm genuinely confused as to what you're trying to achieve?

[Oyster 49]

Yes I’m interested in seeing exactly what the proposals are for a 102 modification, and then seeing the progress.

[headdownarseup]

In order of "madness" perhaps we could go something like this from mild to wild.

This is just an example off the top of my head, you will of course have your own ideas which may be similar or not.

Stage 1= mild clean up to all ports, perhaps even a basic balancing job (if some have done this)

Stage 2= combustion chamber filling (depending on how far we want to go with this) maybe incorporate crankcase stuffing in here too.
(perhaps in here we could talk about the effect of port timing and how "porting and polishing" affects different things at specific rev ranges)
stage 3= custom crankshaft with roller bearings (perhaps with slight alteration to existing crankcases used) maybe with optional stuffing.
(perhaps in here we could talk about perfecting port timing for better performance)
stage 4= bespoke tuned pipe
(perhaps in here we could talk about custom machining to incorporate ideas from other engine designs, perhaps even bespoke casting to allow certain (non-seagull) components to be used)
stage 5= anything else that could be thought of that we haven't discussed yet

The higher the performance gains the more time and perhaps money needs to be spent, so i'm quite cautious to stay within the realms of what the typical garden shed tuner might be capable of with limited tools etc. I think i speak for a great many seagull enthusiasts here that haven't made their thoughts known yet.
Obviously if money is not a concern we can carry on until we've exhausted all of our ideas with custom bespoke components and what exactly is involved with some of this custom machining, where you can get this work done, how much it costs, etc. etc. and whether anyone can really "feel" the performance with any of these modifications. (dyno testing anyone?)

Perhaps we could talk about a boat's hull speed and the relationship that has with a stock seagull against a modified gull and homemade boat and explain why there are certain differences and why we modify certain things to make them better.


Maybe any combination of the 5 stages (we might come up with some even higher states of tune yet) could be used at any time. I'm going to be drawing on you racers for some input here, and not just the Charles's of this world.


We could look at this subjectively and say how high would you like your engine to rev with some of these modifications? (partly my reason to find out how far we can go with stock components)

Basically there are no limits with this thread. If you can think it, we can see (collectively) if it could be done then go and test it out for real. Perhaps even to destruction if necessary.

I've heard people say you can't trust the stock seagull crank past a certain revs. Well, my question is how high is too high before things go wrong? What is it that fails with these? Is it the big end, is it the small end, is it the bronze crank bushes that fail, is it poor crankcase sealing past a certain revs or pressure that causes these bronze bushes to fail and so on etc. Has anyone actually tested a stock crank to destruction before?Same series of questions with the con-rod in all variants from the "classic" engines prior to loop charging. I want to know just how far we can take these old engines and still stay reasonably safe with stock components without everything inside it self destructing into a million pieces and without spending huge amounts of money on what many of us would consider a "throw away" outboard motor to begin with.
There must be quite a few "lurkers" on here that have their own ideas about some of this. If this is true then let's hear what you have to say.
Without knowing where the boundaries are of what could be called "safe" we could all dream up some pretty wonderful ideas here, but without proper testing to see exactly how a gulls components will stand up to this kind of abuse we're not going to know are we?

It's all very well listening to the Charles's of this world, and i do respect what he has to say most of the time, but i can't help thinking that there's some things that need a better explanation of why this or that can't be done unless some other modification has been done.
What are the limitations to using stock components against bespoke (and often expensive) and custom designed parts. How far would you be willing to go with a pile of bits just to say (and prove conclusively) you have the fastest seagull ever? Big balls or not, i want to know

This is the whole point of this discussion here, to see exactly what can and cannot be done in terms of performance improvements to a typical 102 seagull.

Absolutely anything goes here, no limits

If there's any serious racers looking at this and don't wish to divulge certain information, i fully respect that.
But it would be good to hear from your side of things. Anything you can offer we can learn from.

Everything, and i do mean EVERYTHING is welcomed on this thread.

How fast would the typical gull owner want to go? and at what price?



Jon

[NaughtyBits]

What Oyster said. Look forward to seeing your progress, Jon.

BS already found out why & how the ali conrods are not suitable for increasing compression to the extent you seem to be speaking to (as have more than a few ‘racers’). You can see it in the evolution of BS cranks right through to the 5R range.

Again, strongly suggesting you look to use a stronger crank assembly for your project right out of the gate.

Ps. I’m sure Charles would be the first to agree with you not taking his every word as gospel - BUT, he’s built his motors and continues to actually put his ideas to the test (for better or worse!) racing literally across the globe. And he stays in regular contact with those who do the same in New Zealand, Uk, Bermuda, etc. If there’s advice or ideas hinted at you disagree with - build your motors to prove them wrong. Simple.

[Nudge]

Perhaps even to destruction if necessary.

This Is the only way to find out the limit of an engine! It has to be done! If you cant break it, then the part is strong enough Or you have not taken it to that point!

You have spoken lots about the "power head" and not a lot about the gearbox or prop.
With out a good prop you can have the fastest / strongest powerhead and still have no forward "Go"!
I have seen the most shittyest clean up the field simply by having a good gearbox and prop!

[NaughtyBits]

One of our more colourful characters used to race with a necklace made from his broken conrods... it seemed to grow year after year...! Although - things don't always have to break. You want to avoid, just as much, being sidelined every 20 minutes for 10 minutes at a time until the big end cools down enough to get back to working tolerances to run again...

And agree, re: gearbox & prop, Nudge... Given some of what you've said, Jon, re: keeping the 102 'stockish' looking - are you looking to start with keeping the 102 gearbox & work props to suit the RPM range you'll be targeting?