Air cooled bottom end.

[imago]

The more I look at the throwback/draw through build the more I'm wondering if I'm starting with the wrong base engine.

Under consideration now is starting from scratch with the engine build as I have plenty of parts and engines to work with. So if I build from scratch it would be :-

• Higher than 750 ration oil pump gears from @clairetoo
• Low comp forged pistons (Cosworth I believe)
• Strip a crank, new bearings, straight cut primary, welded pins.
• Stronger con rods (make/type TBA?)

Which gives my first question of, anything I've missed from the list? Second question being with all that done what can reliably be put through it hp/torque wise. I'm trying to work out spend vs benefit as I believe the welded crank, checked etc bottom end that I have now is best kept sub-200 hp based on advice from those who know.

As I can do the work here rather than farming it out the extra costs look to be restricted to new bearings, straight cut gears and a set of rods. I have everything else here, or it's already factored in to the build anyway. It'll add a bit of time to the build, but not a crazy amount.

[Duckndive]

I get the fact that you want to use an old skool air cooled motor 

But Use an Oil Boiler  and save a load of £££ and get more beans 

I'll get my coat 

[imago]

7 minutes ago, Duckndive said:

I get the fact that you want to use an old skool air cooled motor 

But Use an Oil Boiler  and save a load of £££ and get more beans 

I'll get my coat 

Agree entirely, For less than half the money I could use the B12 engine I have here and get more out of it. But, the whole point of the build is to use an air cooled motor.

If it was purely about power I could buy a GSXR 1000 or Hayabusa for the same money as a build, map it and piss all over air cooled, oil cooled and most turbo bikes of either flavour.

[Duckndive]

10 minutes ago, imago said:

Agree entirely, For less than half the money I could use the B12 engine I have here and get more out of it. But, the whole point of the build is to use an air cooled motor.

If it was purely about power I could buy a GSXR 1000 or Hayabusa for the same money as a build, map it and piss all over air cooled, oil cooled and most turbo bikes of either flavour.

I get the want to use an air cooled motor i love them and have used them for years but since using an oil boiler it a no contest

EG to do an air cooled crank with straights cuts even if you have the ability to do the work your self a set of new gears is a grand

and every time you take an air cooled crank apart it needs even more weld to keep it together …."the word of a crank builder not mine"

I,m sure you will end up with what you want and enjoy it   

 

 

[Gixer1460]

First question surely is 'what are you looking to get out of it? As this could / can determine what specification will suit. A suck thro aircooled with an HSR / S&S and knee burning dump pipe is about as oldskool as it gets and will do low to mid 200's with a reasonable amount of work (which would be required for a 'good' N/A engine anyway)

But as to your questions - I didn't know any other gears other than the 750 ones were available? It used to be them or stock - no options!. A freshened and preped crank will NEVER be cheap - this is where the oil boilers score! A/C rods, given the choice use 493 marked rods - known as Katana rods originally and used in many racing engines - again the oil boilers get a break as cheap std rods can take substantial hp increases. BTW I have BIG Cosworth pistons in my 1460 engine - not a 'usual choice' but they do the job.

[imago]

37 minutes ago, Gixer1460 said:

First question surely is 'what are you looking to get out of it?

It's not so much about what I want out of it hp wise, sounds daft I know but bear with me. It's more nostalgia than anything as I want a bike like the ones I/we saw in the mags and at shows back in the day but had no chance of being able to afford to build or insure. The other thing for me is that oil boiler swaps/builds have been done to death so to get something 'different' now you need to step back 40 years. Hence finding all the bits (like the JMC) to make it look as '80s as possible then going draw through.

The thinking on the extra work and parts to take the engine up a notch is along the lines of 'in for a penny'. It is an expensive thing, but it's a relatively small addition in the grand scheme of the build. By which I mean if it's costing @ £4k for the turbo and work as planned already, an extra £1.5k could be done if there's a benefit from it.

Numbers wise as it is we're looking at around the 180 hp mark with single figure boost. So given that the turbo is capable of way more, and it's already costed in, the decider for me is how much more of its capability can I use by spending that extra money? 220? 250? 280?

39 minutes ago, Duckndive said:

every time you take an air cooled crank apart it needs even more weld to keep it together …."the word of a crank builder not mine"

The handy thing for me there is that I have five engines to choose from for the bits all runners with know known issues. So I can take a virgin unwelded crank to strip and build up knowing that it's never been welded before. I have all the kit I need to do the pressing and welding, so the cost to me to build a full fat prepped crank is going to be the gears, bearings and rods which I've priced up as £1,200 at current prices. Everything else such as the high ratio oil pump gears is spent or being spent anyway.

Do also bear in mind that none of this (like most projects on here) make a lick of sense to most people, but as a certain Chicken Wizard and collector of noisy, shiny fast things often says :-

"it's what we do"

@clivegto

Edited September 28, 2023 by imago

[clairetoo]

my thoughts are - when I see a 6 second turbo funnybike with a bandit motor , I'll believe they are a stronger engine.....

Welded crank and straightcuts - both essentials , but chuck in a heavy duty backplate for insurance

a full set of top and bottom end heavy duty studs will hold it all together 

as far as I know , there are no stronger rods available - katana rods are said to be the best , but finding a new set today could be a struggle

over-revving is what kills cranks - so a shift light / rev limiter is a good idea , as well as a thorough inspection of the whole gearbox and shift mechanism 

also - sort the oil pickup so it takes its oil from the rear of the engine - stock only works well when slowing down....

acual power level will then depend on capacity and boost - but north of 250 should be easy and reliable 

Edited September 28, 2023 by clairetoo

[Duckndive]

12 minutes ago, clairetoo said:

my thoughts are - when I see a 6 second turbo funnybike with a bandit motor , I'll believe they are a stronger engine.....

Show me a 6 sec Funny Bike that does 4 sub 7 sec passes on the same GSX motor 

And European Record holder runs a GSX1400 based motor 

Even Pro Stock in the US are giving up on them  and going V twin or Mega buck V&H billet 

Its horses for courses and for a road bike a Blandit or GSXR motor is a far better value route 

Totally Unrelated and off topic Get Well Soon 

Edited September 28, 2023 by Duckndive

[imago]

19 minutes ago, clairetoo said:

my thoughts are - when I see a 6 second turbo funnybike with a bandit motor , I'll believe they are a stronger engine.....

Welded crank and straightcuts - both essentials , but chuck in a heavy duty backplate for insurance

a full set of top and bottom end heavy duty studs will hold it all together 

as far as I know , there are no stronger rods available - katana rods are said to be the best , but finding a new set today could be a struggle

over-revving is what kills cranks - so a shift light / rev limiter is a good idea , as well as a thorough inspection of the whole gearbox and shift mechanism 

also - sort the oil pickup so it takes its oil from the rear of the engine - stock only works well when slowing down....

acual power level will then depend on capacity and boost - but north of 250 should be easy and reliable 

Useful info, thanks. 

I missed the studs off the list but they'd be going in anyway tbh. Noted on the back plate, and good call on the limiter/shift light as I hadn't even considered it. The oil pick up is interesting info too.

Capacity wise it'll be 1170, I can't remember the turbo model but the boost capacity was way over anything I'd get to. That's due to the limited options when it comes to carbon seal bearing turbos.

[BillyR]

I feel your pain!

Currently shopping for bits for my big bore ET build, could use a oilbolier or a even better a gsxr1000 lump and have different results..

But.. Its not what does it for me, i just love the sound and presence of a big air cooled motor too much ,so ill just try not to look at the receipts.  

Bit like im also doing ANOTHER full engine rebuild on my V8 Moggie, i could stick in something more modern but that old Rover V8 just makes me smile.

[Reinhoud]

New bearings for a roller bearing crank isn't cheap!! And getting the big end bearings might be a challenge. To get the big ends for my GS1000 turned out to be a big challenge! Lots of companies said they had them, only 2 could actually deliver..

 

Stronger rods were actually quite a bit cheaper than I thought.

I put 493 rods on my GS1000 crank, Had to take 0.5mm off from each side. Order the rods from the Suzuki dealer, costed me 149AUD each, make sure you order the rods with the same colour code!!!! The difference is in the weight.

 

You don't state what bottom you're going to use; a GS1000 bottom with 493  (GSX) rods need a 1mm plate under the cylinders because the rods are longer.

Edited September 29, 2023 by Reinhoud

[imago]

14 minutes ago, Reinhoud said:

You don't state what bottom you're going to use; a GS1000 bottom with 493  (GSX) rods need a 1mm plate under the cylinders because the rods are longer.

That's the trouble with having the project thread and asking questions in the forced induction section, I forget what info's where. It'll be a GSX1100 ET/EX bottom end.

[imago]

35 minutes ago, Reinhoud said:

New bearings for a roller bearing crank isn't cheap!! And getting the big end bearings might be a challenge. To get the big ends for my GS1000 turned out to be a big challenge! Lots of companies said they had them, only 2 could actually deliver..

 

Stronger rods were actually quite a bit cheaper than I thought.

I put 493 rods on my GS1000 crank, Had to take 0.5mm off from each side. Order the rods from the Suzuki dealer, costed me 149AUD each, make sure you order the rods with the same colour code!!!! The difference is in the weight.

 

You don't state what bottom you're going to use; a GS1000 bottom with 493  (GSX) rods need a 1mm plate under the cylinders because the rods are longer.

Just had a look at the rods, basically it's a thousand eruos/pounds for a set of four. The costs are mounting, so I'll price it up properly and run the numbers as well as looking at just how much benefit I'd get from a set of rods. i.e. are they sufficiently stronger to warrant the money, or do I limit the engine to 250hp and stick with the stock rods.

[Duckndive]

12 minutes ago, imago said:

Just had a look at the rods, basically it's a thousand eruos/pounds for a set of four. The costs are mounting, so I'll price it up properly and run the numbers as well as looking at just how much benefit I'd get from a set of rods. i.e. are they sufficiently stronger to warrant the money, or do I limit the engine to 250hp and stick with the stock rods.

Its not HP that kills rods is Tune "Detonation Kills everything" 

Dept on wizzer and carb 250hp on a draw thru is a hoot on the road ...

you rapidly run out of straight 

[Reinhoud]

18 minutes ago, imago said:

Just had a look at the rods, basically it's a thousand eruos/pounds for a set of four. The costs are mounting, so I'll price it up properly and run the numbers as well as looking at just how much benefit I'd get from a set of rods. i.e. are they sufficiently stronger to warrant the money, or do I limit the engine to 250hp and stick with the stock rods.

I paid 149 AUD each for a conrod, at the Suzuki dealer. Don't look at Suzuki Performance Spares, he asks the same in GBP

[Reinhoud]

19 minutes ago, imago said:

Just had a look at the rods, basically it's a thousand eruos/pounds for a set of four. The costs are mounting, so I'll price it up properly and run the numbers as well as looking at just how much benefit I'd get from a set of rods. i.e. are they sufficiently stronger to warrant the money, or do I limit the engine to 250hp and stick with the stock rods.

Do it right straight away!!! With a turbo you can do it accidentally  right, and stuf everyting up, Been there, done that..

[Duckndive]

1 minute ago, Reinhoud said:

I paid 149 AUD each for a conrod, at the Suzuki dealer. Don't look at Suzuki Performance Spares, he asks the same in GBP

If your on facebook ask Joe Marshall down under about rods as the same rods are used in a 2 smoke apparently 

[Reinhoud]

5 minutes ago, Duckndive said:

Its not HP that kills rods is Tune "Detonation Kills everything" 

Dept on wizzer and carb 250hp on a draw thru is a hoot on the road ...

you rapidly run out of straight 

I don't know what went wrong with mine, all it took was F-ing around with the ignition timing and a mis-shift, and that was enouh to destroy the crank case/ con rod / valve cover

[imago]

3 minutes ago, Reinhoud said:

I paid 149 AUD each for a conrod, at the Suzuki dealer. Don't look at Suzuki Performance Spares, he asks the same in GBP

They're 250 Eruro each from CMSNL. 

[Duckndive]

3 minutes ago, imago said:

They're 250 Eruro each from CMSNL. 

Beware of CMSNL   

they say its in stock when its not 

[imago]

8 minutes ago, Duckndive said:

Its not HP that kills rods is Tune "Detonation Kills everything" 

Dept on wizzer and carb 250hp on a draw thru is a hoot on the road ...

you rapidly run out of straight 

Yeah, I was coming at it from the idea that as it's 1168cc and I keep the boost to a reasonable level I don't need to take everything else to the edge to squeeze what I can out of it. It's not going to be some fire breathing 1300 or 1400 cc monster but I reckon from picking out the relevant bits of info I can hit somewhere in between 200 and 250 hp which as you say will be 'quite exhilarating'.  

[imago]

1 minute ago, Duckndive said:

Beware of CMSNL   

they say its in stock when its not 

Yep, been there done that and Robinsons have started that game too (GSXR1100 carb parts). Handy to price stuff up though.

[Duckndive]

Just now, imago said:

Yeah, I was coming at it from the idea that as it's 1168cc and I keep the boost to a reasonable level I don't need to take everything else to the edge to squeeze what I can out of it. It's not going to be some fire breathing 1300 or 1400 cc monster but I reckon from picking out the relevant bits of info I can hit somewhere in between 200 and 250 hp which as you say will be 'quite exhilarating'.  

I used to run about 180 on the road and i could keep up with my mates K6 Thou....the fun started when the straights ended 

[Reinhoud]

https://www.cmsnl.com/products/rodconnecting_1216149302/

[imago]

Just now, Duckndive said:

...the fun started when the straights ended 

That should be an OSS tag line.  

My intention was to stick in the 160 - 200 bracket partly for longevity of the engine, but also because I'm not convinced that either the 42 year old bike or the 56 year old bar holder could cope with much above that.