Throttle Body Replacement

[TimTyler]

All back together again (well, almost...)

Runs great with the default 1.5 turns on the brass screws. No fuel leaks. I'm eager to balance the TB's

Didn't take too many pictures. Too cold, dark and messy. I don't have a garage.

[TimTyler]

The Suzuki clamps do fit perfectly on both the upper bushings and the intake manifolds. My manifold clamp screws are aligned just like RBM's.

Some things I learned...

I noticed when I removed the old manifolds that the screws were just tight enough to be tight. Low torque. Seems the toque value is just 80 INCH-pounds or about 6.5 foot-pounds. I don't have a torque wrench that goes that low so I just used a small hex wrench and got them past-snug. The new manifolds have a circular raised lip on the bottom side with a groove beside that. The lip must be designed to fold into the groove once tightened. The old manifolds had the groove but were otherwise flat. If I were re-installing old manifolds I'd use some sealant like Bill.

Consequently, my old manifolds were still supple and showed no signs of cracks or wear. They must have been installed not long before I bought the bike at 80k miles even though I don't think they're mentioned in the service history. My existing manifold clamps were 46mm screw types (not Oetiker or Suzuki) so I it would seem somebody had done some work on them.

The easiest way to remove and install the throttle bodies is with the airbox (accumulator) attached. Disconnect at the manifolds and the whole thing tilts in/out easily.

It's possible for the injectors to sit too far into the head's injector ports. They can't be connected properly to the fuel rail like this though. So connect the injectors to the fuel rail and then insert everything into the engine ports. Lube the injector O-rings at both ends with fresh engine oil.

The "axle" (where the TPS connects) on the old throttle body is not centered in it's hole on the TB mounting frame. The replacement is centered perfectly.

[TimTyler]

Is there supposed to be adjuster hardware (#3,4,5) on my throttle bracket? There's not. The white plastic end of the throttle cable fits perfectly into the bracket.

Edit: Never mind. I'm an idiot. The adjuster is on the other end of the cable. :hehehe

[Inge K.]

Is there supposed to be adjuster hardware (#3,4,5) on my throttle bracket? There's not. The white plastic end of the throttle cable fits perfectly into the bracket.

These three parts for adjusting the cable is mounted at the upper end.

[TimTyler]

Thx, Inge.

Tried to balance the TB's today. Couldn't get the idle down lower than 1300rpm. Throttle and choke cable both have a little freeplay. Idle set screw on TB is touching it's mark. TPS is disconnected from TB. I even screwed the brass screws in almost all the way. It's weird. If I turn all three screws out one turn the Carbtune balance is stair-stepped at 1300 rpm and gets better as rpm's go up. Carbtune looks grreat at 4000rpm and the engine sounds smoooooth.

I took a propane torch with a short hose all over the TB's and couldn't get the rpm's to change. Air must be getting in somewhere though.

Took it out for a spin and a fill-up. Feels great except for the high idle.

[TS87KLT]

For future reference y'all, Bosch injector o-rings are widely available and cheap.  Online or your LCAPS should have them for under $1 each.

NAPA has 'em for $7.19 at my local  http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Fuel-Injector-Seal-Kit/_/R-MPF312087_0374829705

[TimTyler]

Thanks, Tony. I'll try that tomorrow.

This new-to-me TB has blue factory paint on the main throttle adjustment screw too. Is that unusual?

[TimTyler]

Installed fresh injector o-rings from Napa this afternoon. That definitely helped.

Attached Carbtune and could see that there was still a hint of less-than-smooth coming from cylinder #2.

Removed the spark plugs and they all looked about the same. They have about 25k miles on them. But the spark plug gaps were crazy-big!  :mbird Like almost 1.00mm. They're supposed to be about 0.65mm. Installed fresh plugs, properly gapped. Note to self: Change the plugs once a year, which for me is about every 10k miles.

Runnin' smooth. TB's balance at 1200rpm and keep balance up at least as far as 4000rpm.

I'm calling this job done.

[rbm]

 :easy: Peesy!!  :yippee:

[The Mighty Gryphon]

I don't want to hijack this thread but here is some interesting data regarding plug electrode wear.  According to NGK, electrode erosion in four stroke engines is  0.01~0.02 mm/1,000 km (0.00063~0.00126 inches/1,000 miles.  In wasted spark systems the wear is twice as fast.  10,000 mile intervals is a good choice for at least checking the gap. 

I don't know if it is the Bosch plugs or something else that causes these bikes to eat plugs, but my K75 opened the gap from .025" to .039" on the Bosch plugs in only 8500 miles.  Always had good results with NGK in previous bikes so am trying a set of D7EA's for 2015 to see how they wear.  Just put them in and did a TB balance, so far the engine runs very smooth with good balance with them.  Will have to wait for some warmer weather to really see how they run.

[wmax351]

I don't want to hijack this thread but here is some interesting data regarding plug electrode wear.  According to NGK, electrode erosion in four stroke engines is  0.01~0.02 mm/1,000 km (0.00063~0.00126 inches/1,000 miles.  In wasted spark systems the wear is twice as fast.  10,000 mile intervals is a good choice for at least checking the gap. 

I don't know if it is the Bosch plugs or something else that causes these bikes to eat plugs, but my K75 opened the gap from .025" to .039" on the Bosch plugs in only 8500 miles.  Always had good results with NGK in previous bikes so am trying a set of D7EA's for 2015 to see how they wear.  Just put them in and did a TB balance, so far the engine runs very smooth with good balance with them.  Will have to wait for some warmer weather to really see how they run.

Those are probably car figures. Our bikes fire more than twice as often as a car for a given distance. And they are wasted spark. So between 12 and 24 thousandths. That being said, I should probably check the plugs on my bike when I clean the GPIS tomorrow.

[The Mighty Gryphon]

With three coils on the K75, are these ignition systems running on wasted spark? 

I can understand the difference between a car and our bikes.  My K75RT is like driving around in nothing but 1st and 2nd gear in my car. 

Would be nice if we could get a platinum or iridium plug equivalent in life to what are being used in cars.  Since the EPA regulations of the late 80's all of my cars have run at least 100k miles on a set of plugs with no loss of performance or change in emissions.  Some of these plugs have lasted nearly 200k miles.   

[Inge K.]

With three coils on the K75, are these ignition systems running on wasted spark? 

The hall sensors is on the end of the crankshaft, ie...you have a spark at every revolution.

Would be nice if we could get a platinum or iridium plug equivalent in life to what are being used in cars. 

If I remember correct  :hehehe I've read on other forums that Denso have a iridium type that fits old K's.

[TimTyler]

I took the newly tuned TB's on a cold, 60 mile round-trip slab ride this afternoon to pickup the little idle-screw o-rings from the dealership.

I am happy to report that the engine has never run as smooth as today.  My handlebars have always had a little bit of vibration but that's totally gone now. The mirrors were free from any vibration at all speeds. Looking forward to installing some hand warmers and hitting the road in the spring!  :riding: