1994 Turbo RF build

[peter1127]

100% agree.    NA setups with carbs you do maximum power first to get the main jet done before doing partial throttle/cruising/idle.  EFI turbo the other way around: idle - shakedown runs -  low boost baseline - up the boost bit by bit and adjust/solve if/when necessary

[94RF1146]

Not much exhaust gasses hitting that wastegate!

[Gixer1460]

On 5/19/2025 at 9:34 AM, peter1127 said:

100% agree.    NA setups with carbs you do maximum power first to get the main jet done before doing partial throttle/cruising/idle.  EFI turbo the other way around: idle - shakedown runs -  low boost baseline - up the boost bit by bit and adjust/solve if/when necessary

True, but you should start from a place of safety with a MJ waaaay too large so the engine won't ever go lean @ WOT. 

[peter1127]

5 minutes ago, Gixer1460 said:

True, but you should start from a place of safety with a MJ waaaay too large so the engine won't ever go lean @ WOT. 

Of  course you never want to be crazy lean. But with  9:1 compression and a 5-7 psi wastegate spring a quick dyno run a tad on the lean side doesnt spell disaster. A good dyno operator will back out of a lean run anyway and if not, that is why I stand at the killswitch side of the bike . Safer too if the chain comes off. If  MJ is a stock 125 you can start with a 135  and you normally will already be quite rich. My previous carb turbo bikes both had the stock 125MJ at AFR 11:1. 

 

[94RF1146]

Wastegate relocated.

Now full control of wastegate.

I also lower the coils dwell time from 4ms to 2ms to clean top end misfires.

T&T this Thursday.

[94RF1146]

New MSD 8.5mm spark plug wires. CR10E Plugs gapped at 18 thou. Head torqued to 60 ft/lb. Fresh valve adjustment (cyl 4 were too tight).

220psi dry compression test.

Just realized I can't go to T&T tomorrow, my truck was booked for fuel filter (diesel) and transmission preventive maintenance. 

M.

Edited June 26, 2025 by 94RF1146
Details

[1260Pete1]

19 hours ago, 94RF1146 said:

Wastegate relocated.

Now full control of wastegate.

I also lower the coils dwell time from 4ms to 2ms to clean top end misfires.

T&T this Thursday.

That wastegate placement was fine,  yes ok it's not perfect but shouldn't give any more than a few psi creep, i would say its more in the maxxecu set up, are you using air for boost control or a mac valve?

[94RF1146]

I'm using co2 with 2 genuine 3 ports Mac valves. I couldnt control the boost before, I was maxing out that gtx3576r gen 2.

Also, I dont recommand to put the turbo dead center in the bike. It creates issues (packaging).

Cheers.

M.

[1260Pete1]

10 minutes ago, 94RF1146 said:

I'm using co2 with 2 genuine 3 ports Mac valves. I couldnt control the boost before, I was maxing out that gtx3576r gen 2.

Also, I dont recommand to put the turbo dead center in the bike. It creates issues (packaging).

Cheers.

M.

Have you got any air pressure regulator?  And why 2 mac valves? Something is wrong in the set up but it's definitely not down to the wastegate placement.

[94RF1146]

1 hour ago, 1260Pete1 said:

Have you got any air pressure regulator?  And why 2 mac valves? Something is wrong in the set up but it's definitely not down to the wastegate placement.

Closed loop.

[94RF1146]

Went to the track Friday, got 5 passes. Log says I'm only 45% throttle. I'm 235 lbs butt naked. 

I know, 60ft is terrible. Need to figure out clutch settings.

Still showing some respect to the beast...

On last pass, I spun in 3rd, 4th, 5th.

Now I think I got a spun bearing on cyl #1. Piston hit the spark plug. I got the motor out investigating. 

I had a good time at the track after all. I do this just for fun.

 

M.

 

Edited July 7, 2025 by 94RF1146
Details

[Duckndive]

18 hours ago, 94RF1146 said:

1st pass is best but looks like you rolled off slightly in 2nd half 

hope the damage is not to bad 

Edited July 8, 2025 by Duckndive

[94RF1146]

Opened up the motor...

Looks like It spit a shim on #1A exhaust and massacred the combution chamber & piston.

Exhaust valves are custom. Intake valves are gsxr-1100  31mm grinded to 30mm.

Sleeve has no damage. I got a spare custom piston. Got no luck with this thing!

Sending the head to APE.

I'm ok, just dissapointed.

M.

[1260Pete1]

5 hours ago, 94RF1146 said:

Opened up the motor...

Looks like It spit a shim on #1A exhaust and massacred the combution chamber & piston.

Exhaust valves are custom. Intake valves are gsxr-1100  31mm grinded to 30mm.

Sleeve has no damage. I got a spare custom piston. Got no luck with this thing!

Sending the head to APE.

I'm ok, just dissapointed.

M.

The joy of shims, I'm assuming you have some pretty heavy duty valve springs?

[Gixer1460]

Or you just got unlucky and either touched valves on overlap or simply lost the valve head? Too easy to blame the shims especially as you didn't buzz the motor - I assume you didn't as turbo's are rarely high rpm tools? By the colour of the valves in #1 & #2 - it looks to be using oil?  Strange - 30mm is a 'std' oversize inlet valve and 31mm is a rarity for GSXR - the usual hop-up valve size set was 30/26mm.

Edit - 31mm valve is from a std. watercooled 1100 . . . . explains it, AND they use a smaller dia. stem, so I assume the Exhaust's do as well? More snap prone with turbo temps?

[94RF1146]

I checked valve ckearance 2 weeks ago. Valves were thight on cyl #4 and I set them to specs.

The stock RF valves are 28/24. I'm 30/27. I had a full set of 31mm intake valves grinded down to 30mm. 31/27 didn't have enough valve to valve clearance. 27mm exhaust valve are 100 thou longer than gsxr to fit rf head. RF valves are 4.5mm stem just like gsxr-1100 wc.

Those 7.5mm shims are too small in diameter and are pushed sideways when the cam hit the bucket. Busa has bigger shims to spread the load under the bucket.

I've been fighting this for years.

According to my log, I was shortshifting at 8500 rpm.

In the neantime, I'll get a stock rf head, port it abd de-shroud the valves just to get going. It won't flow as much but I'll be able to enjoy my season.

Edited July 9, 2025 by 94RF1146

[94RF1146]

I'll fix it as I still have spare parts. I want to put it in the 7's and I'm done.

Later, I'll transfer my turbo and ecu to my busa. Right now my 2020 Busa has 34 000 kms.

Edited July 9, 2025 by 94RF1146

[94RF1146]

Contacted APE today... They can't fix it , there is no replacement for the great APE Jay since he passed away last year.

Wally , my local machinist is not equipped for it. I got one more place to try.

I got another cylinder head coming in few days. Gonna dissemble it, clean it, port it, de-shroud the valves and go with this for a while.

Going on a road trip for few days to Jasper and watch CMDRA races in Edmonton (was supposed to take Pamela there).

Back at it on at  my local track in 2-3 weeks.

M.

[ColinH]

12 hours ago, 94RF1146 said:

Contacted APE today... They can't fix it , there is no replacement for the great APE Jay since he passed away last year.

Wally , my local machinist is not equipped for it. I got one more place to try.

I got another cylinder head coming in few days. Gonna dissemble it, clean it, port it, de-shroud the valves and go with this for a while.

Going on a road trip for few days to Jasper and watch CMDRA races in Edmonton (was supposed to take Pamela there).

Back at it on at  my local track in 2-3 weeks.

M.

What needs doing to head? I know a great MX bloke that does many other heads. Machines his own valve seat and guides and also welds / re-machines combustion chambers as the old valves breaking is pretty common 

[94RF1146]

On 7/9/2025 at 1:06 AM, Gixer1460 said:

Or you just got unlucky and either touched valves on overlap or simply lost the valve head? Too easy to blame the shims especially as you didn't buzz the motor - I assume you didn't as turbo's are rarely high rpm tools? By the colour of the valves in #1 & #2 - it looks to be using oil?  Strange - 30mm is a 'std' oversize inlet valve and 31mm is a rarity for GSXR - the usual hop-up valve size set was 30/26mm.

Edit - 31mm valve is from a std. watercooled 1100 . . . . explains it, AND they use a smaller dia. stem, so I assume the Exhaust's do as well? More snap prone with turbo temps?

Piston to valve clearance was done on assembly after degreeing the cams. Valve lash was .028mm on both valves.

[Guest]

On 7/11/2025 at 3:35 AM, 94RF1146 said:

Contacted APE today... They can't fix it , there is no replacement for the great APE Jay since he passed away last year.

Wally , my local machinist is not equipped for it. I got one more place to try.

I got another cylinder head coming in few days. Gonna dissemble it, clean it, port it, de-shroud the valves and go with this for a while.

Going on a road trip for few days to Jasper and watch CMDRA races in Edmonton (was supposed to take Pamela there).

Back at it on at  my local track in 2-3 weeks.

M.

There's a bloke called Dave Lind in Halifax who does some great work on drag engines, mostly HD and GSX but does work on other stuff. It'd be worth contacting him as he knows what's needed for your sort of requirements.

[Upshotknothole]

On 7/10/2025 at 7:35 PM, 94RF1146 said:

Contacted APE today... They can't fix it , there is no replacement for the great APE Jay since he passed away last year.

Wally , my local machinist is not equipped for it. I got one more place to try.

I got another cylinder head coming in few days. Gonna dissemble it, clean it, port it, de-shroud the valves and go with this for a while.

Going on a road trip for few days to Jasper and watch CMDRA races in Edmonton (was supposed to take Pamela there).

Back at it on at  my local track in 2-3 weeks.

M.

Are there any good machine shops left for head work in Washington? I'm down in Portland and the one really good old timer that everyone recommended to me for head work is retired now. 

[ColinH]

On 7/11/2025 at 4:35 PM, ColinH said:

What needs doing to head? I know a great MX bloke that does many other heads. Machines his own valve seat and guides and also welds / re-machines combustion chambers as the old valves breaking is pretty common 

Sorry Chap, just seen you are in Canada so UK not much use 

[94RF1146]

Received my spare RF head today.

Disassembled and cleaned it. Light danage on combustion chamber cyl #1 but will work.

Porting and cleaning up the valves tomorrow. Head had coolant damage (rust). Lapping the valves later then reassembly. Need to modify cam holders to clear cam lobes.

Will be ready early August. 

M.

[94RF1146]

First time I get a cylinder head from Eblag with damage. Won't be an issue as my head gasket bore is bigger.