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Hafrod · Anmeldungsdatum: 28.09.2013 Beiträge: 34 Status: **Offline**

I bought the bike a couple weeks ago and it barely ran at all. It had one coil not hooked up and it had a bad rich condition. I had the carbs off multiple times before buying another pair off another 1983 GPZ 305. With both carbs apart, I noticed original carbs had 140 main jets and the diafram springs were cut in half. I put all the jets and springs from new salvage yard carbs in my original carb. The bike did not want to hardly run at all. I cleaned the salvage yard carbs best I could and blew out all the orifices. Put all their parts back in and bike now idles great and runs fair. My only problem now is, when I twist the throttle, it hesitates (bogs) and then revs. I checked float level and its ok. I pulled my brand new spark plugs and noticed left one was burning nice but the right one is burning white. I have messed with the air bleeds on the side but have not bought a vac gauge to set them. I took it down my block pretty aggressively and in 3rd gear full throttle, it fell on its face but stayed running. Any ideas? Here's things I already did since I got it - it shows 8000 miles on odometer, compression test 144 L and 148 R at wide open throttle, had coils spark tested and ohmed at bike dealership, new spark plugs, plug wires and caps, and boots, changed oil and filter, with bike idling it shows 13.48 on volt meter. Bike is 1983 GPZ 305 USA model red with silver and blue stripes. My father bought me this exact bike when I was 15, owned it about a year and sold it. Now I'm 41 and had a very hard time locating one. Needs total restoration but I restore old cars for a living.

Hafrod · Verfasst am: Sa Sep 28, 2013 4:57 pm Titel:

I also might point out that the bike is hard to take off from being stopped. It acts like its in 2nd gear trying to take off.

Lothi · Verfasst am: So Sep 29, 2013 5:56 am Titel:

Hi Hafrod

Sounds like running on one cylinder

One carb still messy
Carbs out of sync
secondary air on intake manifold; microcracks

You are familiar with constant pressure carburetors ?
Probably pilot air system congested...
pilot air system is especially responsible for speeding up from idle up to 2/3 full gas !

Try cleaning carbs again, using vinegar ! (before -after)
soak carb-case and valves for some minutes, but not more than 5, clean it using toothbrush and after wash with pure water and dry with air pressure)
Especially look at pilot air system and at activation piloting holes for the diaphragm (one bigger and 3 micro-holes)

After cleaning make a coarse adjustment : throttle angle on both carbs should be equal; look through carbs with lamp behind and watch light gap on carbs like controlling eveness of a cylinderhead with a gauge
adjust light gap on both carbs to somewhat 0,1 -0.2 mm ( 0,05 - 0,08 inch), also using idle speed controll (black knob)

Test moving of valve by taking air pressure pistol and very very faintly with low pressure into the inlet (large longish hole on top of inlet):
watch moving valve on both carbs, it should be equal

Mount carbs again and test (again) floater level on both carbs ; plastic tube at drain (near screw on bottom), bending tube upward and controll level: should be 1-2 mm below top of floater case (screws), buut in all cases must be equal on both carbs !

Then try to start engine.
If it is running spray start-pilot or some butane-gas or some drops of gasoline against intake manifold; if rev change manifold has micro-cracks.

If everything seems well now (hopefully) You must use a vacuum gauge to synchronise carbs exactly. Not possible to synchronise "by ear" like on BMW, Moto Guzzi etc.
Without You will always have trouble with full power and speeding up from idle speed.
This bike is such sensitive to synchronization than no other bike i know.
Some user here in forum had bulid low-coast DIY-vaccum gauge
_________________
Grüsse

Lothi tach

Lothi · Verfasst am: So Sep 29, 2013 6:13 am Titel:

Hi Hafrod

Ignition system of a gpz-305 is some "special" CDI:
not running on Battery but has direct power source.
So bike can (theoretically) run without battery (but then DC-regulator will be destruct)
CDI has own load-coil in gernerator besides the 12V coils for battery.
CDI is directly charged with 400V AC from generator !
_________________
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Lothi tach

Hafrod · Verfasst am: Mo Sep 30, 2013 10:39 pm Titel:

Lothi, the vinegar was the biggest eye opener I have done. It cleaned the carbs varnish better than any carb cleaner I used. I tried adjusting the butterflies the same but it seems to have a small bit of play in it. I put everything back together and it had a weird idle again. I adjusted the set screw for both butterfles while it was running and it stopped idlieng odd while I turned it in a little. I think I got it pretty close because the idle comes back down from throttle and it takes throttle. The engine was putting off some heat so I shut it down to cool off. I can't start my restoration till I get it running perfect. I may just have it very close though.

Hafrod · Verfasst am: Mo Sep 30, 2013 11:15 pm Titel:

I just went out and rode it around my house. It now takes throttle very well but it is slow to come back down to idle. Lothi, is this the air bleeds in the side of the carb causing the slow to come down idle? I set both of them out 1 1/2 turns

Lothi · Verfasst am: Di Okt 01, 2013 4:09 am Titel:

Hi Hafrod

Usually air bleeds are not so critical. 1,5 turns is o.k.
Also 1,25.
Controll if needle tip is "sharp"! Sometimes some previous owner with "rustic sense" has overtigthen this filigree screw...
But If rubber seal is missing then You have secondary air which lets idle speed varigate.
And now You have experineced Yourself how sensitve this bike reacts to getting even sligthly out of Sync. ->The drawback of a lean engine with very low fuel consumption to that time.
To adjust sync proper You must use some vaccum gauge !
Slightest touch out of sync one cylinder is pushing, the other pulling.
Even with vaccum gauge You will see both sides dither. You can only adjust to a compromise between unsteadiness in idle and smooth acceleration and slowness with comming down to idle
But if once synchronised it will stay in tune long time.
Only after carb maintenance new synchronisation is nescessary.

But also likely:

Just check manifold for secondary air -> likely for a bike 25 years old.

Maybe also some issue with choke valve and the spring which holds the small acceleration (bypass) valve inside chokevalve closed ? -> typical failure for this carb.
If chokevalve is full opened (horizontal position) these acceleration valves must be still closed and not hang down or flutter from weak spring!
Controll strongness of springs with pushing accerleration valve with a pencil. It must be some kind of strong, You need some force to open.

Last remark:
In my opinion "carb-cleaner" is some way for chemical industry to get rid of expensive toxic waste the easy way and even to get money out of it instad of paying for deposite. Transforming shit to gold Wink

30 years ago some old man told me to use vinegar and I thought "what a nonsense, vinegar for salad in a carb ! Typical befuddled old people" Nevertheless I tried - and was amazed
Only drawback is: not to soak to long !
First it cleans, but after a couple of minutes (>15 or so) it began to corrode copper and brass. Shocked

It's alike HCL acid to loosen rusty screws:
in the first stage it eats all rust in the bolt thread but operating too long it began to corrode again.
_________________
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Lothi tach

Hafrod · Verfasst am: Di Okt 01, 2013 10:10 pm Titel:

OK, today I installed brand new intake rubber boots and o-rings. I also installed both o-rings and washers for the air bleeds. All are brand new KAWASAKI parts. I eyeballed the butterflies to the hole in the venturies making sure you can barely see the edge of the hole. Reassembled and it still comes back down slow to idle. Engine is at temp. The filigree screws look new. These carbs had the factory plug still in them. The throttle cable is not sticking and the slides for the diaframs feel nice and smooth.

Hafrod · Verfasst am: Di Okt 01, 2013 10:41 pm Titel:

Where should butterflies be set? There a 3 little holes. Should I set it with the first hole barely visible?

Hafrod · Verfasst am: Di Okt 01, 2013 10:44 pm Titel:

I checked the spring loaded flaps in the choke butterflies. They seem to have spring pressure. When turned vertical, with choke off, They don't hang down.

Hafrod · Verfasst am: Di Okt 01, 2013 10:45 pm Titel:

I do not understand how to check diaframs by blowing air into the carb. Where exactly do I blow a small amount of air in?

Lothi · Verfasst am: Mi Okt 02, 2013 9:59 am Titel:

Hi
To make rough check of butterfly position turn to idle position and hold a lamp/torchlight behind carb ( motorside).
Look from inlet side through "closed" butterflys and You see a small ligthgap shining through edge bottom of butterflys
This should be equal on both carbs

Underpressure/moving valve(diaphragm check):
Blow softly some air into oval hole ontop of choke-side ,see Your last picture
_________________
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Lothi tach

Hafrod · Verfasst am: Mi Okt 02, 2013 6:33 pm Titel:

Lothi, I'm waiting on a phone call of a local bike mechanic to come over and sync my carbs. I tried different things yesterday just to see what would happen. I had tried the short diafragm springs and nothing changed. I also jetted the main jet from 130 to 140. It did not run good at all. This morning I removed the carbs and put all the stock jets and springs back in. The bike fired up and was idling good. I let it idle a couple minutes on choke. It has the bog or hesitation back. I turned the mixture screws on the side out to 2 1/2 turns and it helped a little. So now its got hesitation but not staying at 4000rpm after revving it like yesterday. Why is this so on one day and off the next? What causes off idle bog and/or hesitation? Could this be a valve adjustment? The butterflies are set the same on both. I'm sure your right about the carb sync so hopefully the guy will come here and set it. I was just curious on valve adjustment because I have not looked at that yet. I looked around on the site but never found the valve clearances and how to do it. Can you link me a how to? I've never adjusted motorcycle valves before. I do have feeler gauges and see the 4 plastic hex bolts on top of the cylinder head.

Lothi · Verfasst am: Do Okt 03, 2013 6:05 am Titel:

Hi Hafrod

Valve clearance:

Inlet 0.17 -0.22mm
outlet 0.21 - 0.26mm

If You have experience with valve clearing on motor-engines with OHV and rocker lever than it is the same with this bike, no rocket science.

Changing main jets 130 <--> 140 should not make much difference

Different diafragm springs sounds curious, I never heard or seen of.
Different valve-length, yes. It is (german) 27 hp version and internat. 34 hp versions http://www.gpz-305.de/Tipps/Tuning/Vergaser.html

If engine is cold and choke activated it runs on high revs (3000-4000), that is normal and could have unforeseen "effects" for unexperienced riders / newcommers when starting on a ride Wink

What me confuses a little:
problems with coming back from high revs is usually typical for problems with sync as for some unwanted secondary air (air jet, manifold motorside)

Unsteadiness is something different:
Typically "produced" by carbs out of sync
But also can be electrical problem by "ratteling" sidestand-switch and/ or corroded cluth lever switch.
Here in forum some users had reported problems with "rattling" side stand switch contact which produces unsteadiness in idle and turning up in lower revs, but not in slowness coming down from higher revs. Specially when engine is vibrating in lower frequency like running in idle
On high revs the "rattling" of this sidestand-switch seems to "equal" and enginge is running fine then.
Sides stand switch belongs to the "matrix" which turns motor off if You try to take off with sidestand down (CDI ist "switched" off)
Sidestand switch; clutch lever and neutral gear are "matrixed" via simple diodes and as result the "output" of this "matrix" is a ground signal to CDI if everything is o.k.
Look at CDI, find "extra" single cable contact and decollate contact, put CDI-Side to "ground" (frame). contact = grounded -> engine running.
_________________
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Lothi tach

Lothi · Verfasst am: Do Okt 03, 2013 6:21 am Titel:

You can do a rough test to find out wether left side or right side is causing the trouble:

Warm engine up.
Adjust idle speed knob to somewhat 3000 - 4000 revs or fix throttle to that.
stop engine, remove one spark plug and put some spare spark in it, not to operate igniton without load (could destroy CDI); dont't forget to ground contact spare spark ot chassis.
start engine again
Now it should run about 1000-1500 revs with one cylinder.
If fixed by idle speed knob then try to open throttle
-> It is somewhat tough like gum, but should speed up

Do it the other cylinder
-> it should be equal in behaviour

If not starting, not speeding up or different/lower revs in "idle" then:

carbs are out of sync
different fuel level in carbs
cylinder have different compression
problems with exhaust (one blocked by rusty pieces inside; check with hands on exhaust outlet on both sides when running on both cylinders),
valve clearence highly different (but this should be heared)

Some other cause could be: lower compression on one cylinder !
_________________
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Lothi tach

Lothi · Verfasst am: Do Okt 03, 2013 6:53 am Titel:

General hint for electrical contacts for this "old" bike:

Usually contacts began to corrode after some years
Especially looking at your bike which seems have been some playground for bird and chicken:
-> very likely some contacts are corroded.

General hint:

Buy some white, acid-free vaseline for human use from pharmacy.
Apply on every contact You open and close.
If contact is visibly corroded then use some Q-tip for ear cleaning and clean contact using vaseline. In obstinate cases You can use "Ballistol" weapon oil, but no other brand (other may destroy isolation of wire)
White acid free vaseline is neutral to electrical power, conserves contacts against future corrosion and undercuts rusts, also blocks future water or moist.
Never use "contact cleaner": it removes corrosion, leaving blank metal which corrodes in a short time more worse than ever bevore. Even if advertised as "long conservation" or other nonsense . Contact cleaner is just for a short-time effect !
White vaseline = terminall grease. Identical from chemical content, just different price Wink

Silikone is different and can cause problems by isolating "too much" the unwanted way and causing trouble if applied accidently on paintwork (must be removed, expensive act before re-painting)
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Lothi tach