Topic: CB 836cc f1 turbo - spoked kickstart street turbo

[PeWe]

150 rear tire! I have 110 (4.0-18) rear on my K6

[Ilja]

150 rear tire! I have 110 (4.0-18) rear on my K6

I have 110 on the front at the moment! 😄
(2.50 rim)

[PeWe]

150 rear tire! I have 110 (4.0-18) rear on my K6

I have 110 on the front at the moment! 😄
(2.50 rim)

I have 100/90-19 but plan smaller next time. 3.25-19. Std sizes. My rear before was 120/90-18 but became flat really quick before 4000km and horrible handling in corners. Break-in of my new 1005cc pistons might helped the rubber to disappear

I have read that the std rims need tires that match for best handing. Std rims, std tires. Now H speed class rear, before V. Maybe H rubber last longer?

Your rims however will house wider tires!

[Ilja]

150 rear tire! I have 110 (4.0-18) rear on my K6

I have 110 on the front at the moment! 😄
(2.50 rim)

I have 100/90-19 but plan smaller next time. 3.25-19. Std sizes. My rear before was 120/90-18 but became flat really quick before 4000km and horrible handling in corners. Break-in of my new 1005cc pistons might helped the rubber to disappear

I have read that the std rims need tires that match for best handing. Std rims, std tires. Now H speed class rear, before V. Maybe H rubber last longer?

Your rims however will house wider tires!

Yeah thing is with spokewheels you need tube type tires because with tubeless radial tyres the sidewall is very soft and this deforming eats your inner tube a bit.. So no fancy state of the art rubber..  .

On the front I have a pilot active 110/18 tube type tire since the front is most important... xD and on the rear a pilot road 150/17 tubeless with tube and with a higher sidewall to compensate for the 17" rim size. I ordered that pilot road wrongly for my xr650r sm a few years back, should have been a pilot power... so now I could finaly use it up. 😄

[seanbarney41]

Ilja, would love to see some pics and a little about your Kawasaki's if you get a chance sometime.

[Ilja]

Fabbing up spacers and modding disc pattern for cbr900 discs on stock cb750 f1 front hub.

[Ilja]

Well I have a z1r project and the z650 turbo.. which has a gpz750 turbo engine which is basically a beefed up z650 lump.
Stock crank stock rods stock factory undercut gearbox, stock 1984 fuel injection, powercommander hooked up to the boost sensor, intercooler, gt2056 turbo, 150-200hp, external wastegate, 35mm tb's, stock cast 7.8:1cr turbo pistons, saab 2.0 350cc injectors and lockup clutch.
It lifts the front in 2nd at 15psi.. and also in 3th and 4th sometimes. If I switch to 20psi all hell breaks loose.😂

But its a dog offboost, flat and little torque (below 4000rpm, low compression motor and high gearing)... but then at 5500rpm it suddenly makes 100hp more and flies to 10.000rpm. Likes revs... 54mm stroke (9mm less then the cb750!!)
Needs an 810cc turbo wiseco kit...

I actually like the cb750 better to just tour everywhere since it performs close to stock offboost and turbo comes in at 3800rpm. It has less topend but more low and midrange. 63mm long stroke really makes the difference.... 😄
And with the carbs its almost a stock bike regarding reliability...
 I really trust it to bring me home. 

[Ilja]

Not sure yet about the intercooler... 🤔
Might leave it on for a while, doesnt hurt.. 😄

[seanbarney41]

Really cool #$%*, ilja.  I've got a couple z650s too.  One has 710 wisecos and megacycle cams.  I really like em both.

[ivanhoew]

on the 650 Ilja , maybe try the gt1752 saab turbo , much better bottom end on the turbo mini , the 2056 allways seems to come in 2k rpm later .

regards
robert.

[Ilja]

on the 650 Ilja , maybe try the gt1752 saab turbo , much better bottom end on the turbo mini , the 2056 allways seems to come in 2k rpm later .

regards
robert.

Hey Robert,

Yeah, it will probably be a bit more responsive but actually its not really bad.. not that its 2k late or anything.
Maybe you had a different one on the mini?
Before I had a T25 which was really laggy... boost after 6000 rpm.

I bought the gt2056 turbo new a few months ago and it actually also starts to spool at 4000rpm.
It just takes a bit longer to reach boost, but thats maybe also a bit because the z650 has 750cc and the plenum is bigger.
But the z650 is quite bad mainly below 4000rpm, probably also because of the high gearing...hehe.

The GT1752 on the Honda spools at around the same rpm (3800-4000rpm) but it just lags less and has the preset boost before 5000rpm. But also the Honda pulls better below 4000rpm.

The gt2056 and 1752 are not that different... bigger exducers but similair snails. 😄

[ivanhoew]

on the mini the turbo i have is the gt1752 with the 38.55mm inducer , off the saab 9.5, 0.48 a/r turbine housing , with 1310cc i get boost at 1800 270 degree cam ish comes in a 2300 and10 psi boost by 2800.  i run it up to 23 psi spike and 19 psi steady state ...with quite a large intercooler . in the turbo mini world we have cars with the 2056 on them , and they always seem to need a good 1k to 1.5k more  rpm to reach the same boost . i am guessing the 56 mm turbine wheel has a slower air speed in the housing per volume of gas .

on the 400/4 i bought a new ihi rhb5/1 with a 32mm inlet , with a p7 turbine housing  it had boost at 7200 ,with a p5 it came in at 4800 , boost climb was v fast ,  it went from 10 to 15 psi in 500 rpm , peaking at 85 bhp at 8500 ,when the clutch gave up ,  it should have peaked at 10k .

regards
robert.

[Ilja]

on the mini the turbo i have is the gt1752 with the 38.55mm inducer , off the saab 9.5, 0.48 a/r turbine housing , with 1310cc i get boost at 1800 270 degree cam ish comes in a 2300 and10 psi boost by 2800.  i run it up to 23 psi spike and 19 psi steady state ...with quite a large intercooler . in the turbo mini world we have cars with the 2056 on them , and they always seem to need a good 1k to 1.5k more  rpm to reach the same boost . i am guessing the 56 mm turbine wheel has a slower air speed in the housing per volume of gas .

on the 400/4 i bought a new ihi rhb5/1 with a 32mm inlet , with a p7 turbine housing  it had boost at 7200 ,with a p5 it came in at 4800 , boost climb was v fast ,  it went from 10 to 15 psi in 500 rpm , peaking at 85 bhp at 8500 ,when the clutch gave up ,  it should have peaked at 10k .

regards
robert.

Hmmmm I think I have the same GT17 on my cb750, straight of a saab with .48 ar turbine.
I also have a destroyed one somewhere which has a different turbine wheel with one blade difference.

The GT2056 on the kawa has a .46 turbine housing and the outside snail size is actually quite identical to the GT17.
But yeah indeed it has a 56mm turbine, but still its quite close to GT17 performance with regard to spool when I compare the honda and the kawa. Both start around 4000 and are at boost between 5000-5500ish rpm.

I can't really compare it 1on1 as the engines are different displacement, stroke and cam... the GT17 would probably lag less and hit a bit earlier but the GT2056 so far feels like an awesome turbo which can be bought new for 475,- euros.

I think the GT2052 is quite similair to the GT17 and can also be found new.. according to the compressor maps its less efficient above 15psi but more responsive if you never go over that boost pressure, also a nice alternative when looking for a fresh one.

[Ilja]

Apart from some minor front end things not much happened..

Waiting for some long bolts to mount the discs and im kinda looking up against opening the engine again, installing sleeves in the inner stud holes to close the stud crank case breathers, having the cylinders honed for the MTC 836 pistons and wasting another expensive MLS gasket. 

But I'll take it apart tonight anyways. 

[Ilja]

This is what needs to be done to seal oil and vapour from being blown up through the F1 barrels and out of the area around the inner studs on the F2 head.


By the way for anyone that needs it, theres a 1030cc turbo piston kit on ebay for a reasonable price.
I seriously doubt pushing the poor cb750 bottom end even more and spinning heavier pistons is a wise thing to do, so I'm going to try and skip on that kit.. hehe.

If you have a hyvo engine with carrillo rods, that 1030cc kit with a turbo.. would be a killer engine. 
I think 140nm torque would be possible.

[Ilja]

Well the turbo looks to be burning clean...

[Ilja]

The f2 head issue when combined with the f1 or K barrels!!
Basically those holes are engine breathers when not sealed..

[Ilja]

Not a scratch.... 😄😄   
Cruzinimage 125 dollar kit with up to 15psi boost!

To switch for MTC or not to switch.... 🤔 hmmm

[Ilja]

Crap... cant use the MTC pistons..
They are 64.92mm and my old pistons where 64.99-65.00mm.
Too much piston clearance would be the result.
Also the MTC deck height is 1.25mm less! So that would mean 2.5mm squish compared to 1.25mm at this moment. And below 7:1 compression..
The squish band is not big, basically only resulted from the +4mm bore but it still should add some turbulance around the edges... where detonation occurs.

I could install them without a base gasket but that would only gain me 0.5mm.. 

Oh well... lets close the stud holes and put everything back togheter.

[Medyo Bastos]

do you need a set of pistons?  i can check a few different sets if you like? i might have a set that would work for you.

[Ilja]

do you need a set of pistons?  i can check a few different sets if you like? i might have a set that would work for you.

Hey there...thats nice of you!
Crap I only see this message now.
Engine is completely back togheter and running like a sewing machine again.
Do you happen to have something like the cruizini 836cc kit but forged?


So engine back togheter with the same MLS gasket+locktite5910 and studs sealed up with some o-ringed dowels I made on the lathe.

I found out my old wastegate actuator already cracks open at..... 0.1 bar!! and is completely open around 0.7 bar.
The boost always ran back a little at higher revs also...makes sense now. It did 0.5 bar or 7psi with that one without a boost controller.

I had a new 1 bar wastegate actuator on the shelve off the gt2056 which I recently bought for my k*wasaki and that one starts to crack open only at 0.7bar!

Soo I installed that one and im very curious what will happen now! The old one might have been pushed open by exhaust pressure alone..

Need to fix the brakes lines and the front fender and then I can finally go for a ride again.

[Old Scrambler]

Looking real good

I assume you installed an o-ring at the bottom of the new 'dowels' just a bit thicker than the base gasket.

[Ilja]

Looking real good

I assume you installed an o-ring at the bottom of the new 'dowels' just a bit thicker than the base gasket.

Yeah the dowels have an oring on both sides and fit in the holes where the original dowel pins with large rubber rings where with the stock head gasket.
The mls gasket has a smaller hole here and pushes against the small oring, sealing the stud hole.

[Ilja]

Looking real good

I assume you installed an o-ring at the bottom of the new 'dowels' just a bit thicker than the base gasket.

Like this:

[Ilja]

Ohh almost! Only the front fender, rear brake cylinder, brake fluid reservoir mount, speedometer, new chrome gauge clock covers left to do!