1981 Kawasaki GPz550: Restoration

[SVSooke]

Very cool indeed,you help keep me going on my 82 750:encouragement:

 

[Rob S.]

"I would like to be done by June..."

Only missed by a month!

Very nice.

 

[srsupertrap]

"I would like to be done by June..."

Only missed by a month!

Very nice.

by a month and two years but who is counting . . . Couple of more pics & question

PS: Unfortunately it didn't start when Ray came over On Saturday over to shoot the video. We had spark, starter spun the motor way fast but on Prime gas overflowed out the carb drain lines and when I pulled plugs from cylinder 1 & 4 they were completely dry? Initially when starting we did hear it backfire through the exhaust.


Stranger yet the floats are plastic so I assume they are non-adjustable and they can only be installed one way. Perhaps the idle adjust screw needs to be turned in to lift the slides a bit to get it started. I am missing anything?

 

[Guest]

Steve, They should be adjustable by bending the brass tab that rests on the float valve. If they are 29s thee level is 23 mm from flange to float bottom when inverted. This should give you a fuel level 4 mm below the flange in service. You can make a test device using a spare drain plug, a small metal tube pressed into a drilled hole and connect a fuel line (clear). Ray

 

[Guest]

Sorry, I missed your call. I've been doing a bit of looking at posts talking about level problems on flatslides. There is one by Skip titled float level Mikunis flatslides? Dated 6-26-2003. It may be pertinent. Really strange!

 

[srsupertrap]

No worries Ray, I am probably close to giving it another attempt to start it.

When Ray & I attempted to start the GPz two weekends ago gas overflowed from both overflow lines which was likely caused by dirty or worn needle valve assemblies. The following Monday (7/25), I contacted several Mikuni distributors including Tucker Rocky (worthless), Orient Express & Sudco to see if any of them could source parts for these Mikuni RS27 Smoothbores predecessors of the present day RS34, RS36, RS38. Jon Walcher from Sudco took the most interest considering the easy answer was No. He mentioned another employee, Chad who was currently out of town had some 25 years experience @ Sudco might be able to help point me in the right direction but was not due back till 8/1/16.

In the meantime, I Googled for Mikuni RS27 smoothbores a bit and found this GS Forum thread came back on the top of the search hits . . . not very helpful. I started a parallel thread on the GPz550 Forum back in Jan 2014. While maintaining that thread, the Administrator Corey Clough who raced GPz550s in the Bay offered to sell a set of RS27s which he bought from another GPz forum member. Corey didn't like the RS27s and never installed them on his race bikes. He mentioned the throttle cables had to be custom length. Corey was very helpful on my GPz project . . . sorta like a Nessism for the GPz550 community. Regardless that some of the background for the following picture.

My leaky RS27 on the right and another set of used RS27s I bought from Corey Clough on the left.

A picture is worth a thousand words. The RS27 float are plastic and probably not meant to be adjusted. My floats are the bright yellow ones. Notice the tab/tang has curled on the float right on the right. The brown one has no deformation (WoHooo)

Everyone knows the strategy now, time to swap bad for unknown and see what happens. That is until Sudco replies. Jon Walcher mentioned these RS27s might have been made for the Japanese market only?

I swapped floats first because I am conservative. I found several of the float pins were gummy because in 2015 I filled the carbs but never started it . So I cleaned them again. The float height with the RS27 inverted is approximately 14.25mm

This picture illustrates the warped float tab. I probably will try to bend them back with heat at some point.

I have now swapped all the floats into the RS27s that will be reinstalled on the GPz550. In the foreground, I swapped out the pilot jet (30s - I am at 5000+ Ft) and replaced them with the 32.5s which were originally installed. I also adjusted the air screw from 1 full turn out to 3/4 of a turn out based on my second set of RS27 because Corey stated they came off a running bike.

Could definitely use any Forum help here because you never know what is lying around from previous projects etc. These are the leaky Mikuni Needle Valve Assemblies. The Needle Valve body measures the following

Ht: 10mm & OD 8mm. The body is marked like jets with a Mikuni symbol 2.0

Leak testing this last Saturday . . . very high-tech

Looks so sweet but they still leak from Carb 1 & 2. Back to it this time though, I swap the needle valve assemblies with better results. No leaks this time.

 

[Nessism]

I like the test stand. Checking fuel level with the carbs off the bike saves a LOT of frustration later on.

On the last few sets of carbs I've done I've gone to automatically replacing the float needles. The needle springs get weak and then the fuel level rises. To clean up the seat I take a small piece of gray scotchbrite that has been worn down some already and stuff that inside the seat, then I take a wood stick and spin the scotchbrite around until the seat is bright and shiny where the needle contacts.

As an aside, regarding those plastic floats, I bought a low mileage Kawasaki ZX6E a number of years back and found one of the floats full of fuel. I bought a new float and threw the old one on the workbench. Now something like 7 years later the float is still full of fuel. Not one iota has escaped or evaporated. Makes you wonder how it got in there in the first place.

Looking forward to the upcoming start up video. Hope the jetting is reasonably close so you can get that bad boy out on the road!

 

[srsupertrap]

I like the test stand. Checking fuel level with the carbs off the bike saves a LOT of frustration later on.

On the last few sets of carbs I've done I've gone to automatically replacing the float needles. The needle springs get weak and then the fuel level rises. To clean up the seat I take a small piece of gray scotchbrite that has been worn down some already and stuff that inside the seat, then I take a wood stick and spin the scotchbrite around until the seat is bright and shiny where the needle contacts.

As an aside, regarding those plastic floats, I bought a low mileage Kawasaki ZX6E a number of years back and found one of the floats full of fuel. I bought a new float and threw the old one on the workbench. Now something like 7 years later the float is still full of fuel. Not one iota has escaped or evaporated. Makes you wonder how it got in there in the first place.

Looking forward to the upcoming start up video. Hope the jetting is reasonably close so you can get that bad boy out on the road!

That would be nice, Ed if you get a minute could you post a picture(s) of how you use gray scotchbrite to clean inside the seat. The ID of those pictured are pretty small. So far no response from Sudco concerning replacement needle vale assemblies so it cannot hurt to try and clean what I have right now?

 

[hillsy]

I've had luck in the past with spinning up the float valves in my drill press and dressing them with some wet and dry (600). As long as they are not too dimpled it will take the shine off them and make them seal better.

Nothing better than getting new ones though......

 

[Nessism]

Here you go Steve. The process involves scrunching up the piece of scotchbrite (I used Gray), shoving it inside the seat, then twisting the scotchbrite while shoving it inside the seat. Once it bottoms out then push hard on the scotchbrite while spinning to polish the seat. Optional is take a small screwdriver or piece of wood and use that to shove the scotchbrite inside the seat while turning.

Hope this helps.

P1030171 by nessism, on Flickr

P1030172 by nessism, on Flickr

P1030173 by nessism, on Flickr

 

[Guest]

Looks like you are heading in the right direction. Looking forward to see it run.

 

[srsupertrap]

Thanks Ed for posting those pictures, that helps.

Ray, I reinstalled the carbs, the float bowls are full and it hasn't leaked this week. I will try to start it tomorrow. If you have time Sunday maybe we can try again and shoot that video?

Regarding the carbs, I contacted Sudco on Friday to follow up on my request for parts. Chad Thompson who has been at Sudco for decades was very insightful & helpful, I learned these carbs are actually called TM27s. Chad stated all Mikuni Flatslides are in the TM family even the present day RS 34-40 series. These TM27s were manufactured in 1986 & 1987 and were pretty quickly obsoleted. When I asked about replacement TM27 Needle Valve Assembly, he told me I was most likely out of luck because they couldn't find any with an OD of 8mm. He was more hopeful though they could find some replacement float needles. I have the action to create a drawing with the dimensions and email it to me on Monday.

That's the latest update. We will give it another whirl Sunday

 

[Nessism]

Looking forward to an update...

 

[Guest]

Any news Steve? Possibly cam chain adjuster loosened up? Ray

 

[srsupertrap]

I will start with the good because there is some BAD to follow.

Regarding needle jet assemblies, I sent Chad Thompson @ Sudco a TM 27 needle valve assembly and he identified Sudco's P/N VM15/172 as an equivalent needle. No luck on the needle seat and each one cost about $25 and there is no returns. I have asked Jeff Tuttobene to see if anyone at Mikuni can help but no definite word yet.

Jeff saw my picture of my butchered Dyna S wiring connections below and offered to help . . . again just like so many others have. When one installs a Dyna S on 81-83 GPz550's you loose the IC Ignitor and the factory connector. Note the extra Dyna S wiring loop.

Jeff lent me his Super Crimper, gave me his extra OEM connector to make my Dyna S connections look professional

Much better

 

[srsupertrap]

After getting the Dyna S statically timed on Saturday 8/13, I hit the starter button and it fired right up. I only let it run for 30 seconds because the fresh engine paint, new rings etc. but the GPz was very responsive which is likely attributed to 1/4 turn throttle. I blipped it a couple of times to 3-4K and shut if off feeling good. Later in the afternoon I started it again but it seemed less responsive to the throttle & noiser. Didn't over analyze it . . . perhaps I should have.

Next day, I called over Ray (Ghostgs1) to take a video confident it would start but when we started there was a real loud knocking noise coming from the valve train but we couldn't make heads or tails which side the noise was coming from. So my assignment for this weekend was to remove the valve cover, check the valve lash and see if anything hand grenaded inside. Once you remove the valve cover on a GPz/Kz550 you have to remove the cam chain tensioner which in my case requires removing those Mikuni TM27 . . . Ugh

It didn't take long to find this, while removing the spark plugs I found the insulator on # 1 spark plug had broke off inside the engine while it was running. No mechanical contact with the spark plug. First time I have seen this and the spark plug was brand new NGK.

Here is a picture of a .022" feeler gage that I slipped in between #1 Intake valve .. . that's a problem because the OEM valve lash is suppose to be .006" to .01" for the intake & .004 to .008" for the exhaust

I figured I better fish out the remains of the porcelain insulator form cylinder #1. I found some real small threads of porcelain insulator but nothing really visible. I stuck a carb vent line down the cylinder to see if I could suck up the remains but no luck and not very tasty either. After a lot peering down the spark plug holes I could not find the remains of the insulator. What I could see of the valve appeared to be undamaged but no telling if a piece got stuck under the seat which may account for that huge .022" valve lash measurement

I then went back and checked the valve lash and this time all the valve lash measurement were within spec. I guess my question at this point is can anyone convey their experiences with a broken spark plug porcelain insulator? I know its brittle but I have not idea whether a sound approach would be install a new spark plug and see what happens. Otherwise I am looking at tear down to the cases and replacing all those gaskets again.

PS: I also found a couple of the Yosh Exhaust stud nuts were loose which may have contributed to the noise

 

[Nessism]

Steve,

You do not need to remove the tensioner, just the spring cap. A 17mm socket on a long extension will allow you to reach the cap. Pull off the cap & spring and then pull back on the cross wedge just enough to make sure it's not jammed in tight. Do this just before you reinstall the valve cover, not while working on the top end. You need the tensioner in place while rotating the engine and so forth.

Regarding that insulator chunk, I'd make a solid effort to try to find it, or at least clean out the cylinder. Take a piece of hose small enough to fit down through the spark plug hole and connect it to your vacuum cleaner and try to suck out the debris in the cylinder. That ceramic is hard so you gotta get it out of the cylinder. If you can't find it that means it's gotta be in your exhaust system.

Good luck

 

[srsupertrap]

I found this on the NGK site but no guidance about what damage occurs

The combustion temperature can rise to an abnormally high level so that heat transfer from the interior of the plug is unable to keep pace, leading to trouble such as cracking of the insulation and melting of the electrodes.

[TD="class: small"] 1) [/TD]
[TD="class: small"] Breaking of the insulation Type 1 (See Photo 1)

• When selecting a plug, make sure that the standard plug will not go outside the optimum temperature range while engine combustion is normal (refer to the "Plug Temperature and its Effects" chart below). If for any reason (water leakage, oil leakage, etc.) the engine starts knocking or detonation occurs, the temperature of the combustion gas will rise sharply and the plug, piston and valves will overheat. Overheating of the plug causes the center electrode to expand, and this can break the insulation.

[/TD]
[TD="class: xxsmall"] Photo 1: Breaking of the insulation

[/TD]

[TD="class: small"] 2) [/TD]
[TD="class: small"] Breaking of the insulation Type 2 (See Photo 2)

• This is the situation where deposits (products of combustion of oil, etc.) penetrate into the gap between the center electrode and insulation at the firing end, expanding the center electrode and causing the insulation to break.
• Normally, deposits do not penetrate into this gap. If the engine overheats, the engine's cylinder head may distort. This means that cooling of the combustion chamber will fail which in turn means that knocking will occur more easily. Repeated knocking leads to abnormal pressure and vibration in the combustion chamber. This abnormal pressure and vibration causes the deposits that have accumulated in the combustion chamber to scatter as fine particles and enter gaps in the plug.

[/TD]
[TD="class: xxsmall"] Photo 2: Entry of deposits

[/TD]

 

[Nessism]

Steve,

You only ran the engine for a few mins while in your garage. No way a fault in your engine caused that plug to break.

 

[Guest]

Wow! I have never seen that before. I second Ed's vacuum cleaner suggestion, ceramic in the ring area could be very damaging. Sorry to hear that. Ray