www.gpz-305.de

Blue cod · Verfasst am: Mo Nov 15, 2010 8:53 pm Titel: Bike does't start/ cuts out

Hi Lothi,
I'm in England and have viewed your website with interest.
I too am the proud owner of a 1980s Kawasaki Gpz 305.
Today on your forum someone has had the same problem I have with my machine http://www.lothi.org/forum/gpz-305/viewtopic.php?t=1039
Your advice is spot on.
My bike has had carburretor problems, due to not being used for 13 years(engine seizure, only just got round to rebuilding the engine) and also because of the rusty tank.
I also use a carb cleaner in a spray can(aerosol), if this is sprayed into the jets etc you can see where the mist exits....this can help identify if their are any blockages remaining after cleaning.
Tomorrow I will put the carbs back on the bike and see if it finally starts and runs properly. Since the rebuild the bike has not idled properly and tended to cut out when the revs dropped, died and wouldn't restart.
The mechanic that helped with my rebuild confirmed that the carbs were the problem, the old fuel had gummed up(blocked) the jets and fine drillings in the carb body.
Just out of interest, there is a website UK dedicated to Kawasaki twins which has members over Europe and the United States of America....it doesn't have many members who are owners of the Gpz 305 though, that bike was more popular in mainland Europe than the United Kingdom:

//http://www.armbell.com/kz400/viewtopic.php?t=113&mforum=kz400

The Kawasaki kz400 seems to be the most popular bike which people have on that forum, though there are some 305 owners....a lot of the custom bikes being popular in the USA.

As I am not a member of your forum and my German is woefully inadequate to participate in it, I thought you may want to let your forum member know about the carb cleaning aerosol which may identify if there is still a blockage in his carbs.
Wish him luck with getting his bike running again and keep up the good work on your website.

Blue cod · Verfasst am: Mo Nov 15, 2010 8:56 pm Titel:

My bike's problems could be due to more than one problem as Lothi suggested but I'm not entirely sure what.
Managed to get the bike running today and it no longer cuts out when the revs drop and now restarts easily enough(either hot or cold) after stalling or switching off the engine.
Although I adjusted the idle speed down to 1500 rpm it has risen to nearly 2000 rpm when ridden for ten minutes or so, consequently I will have to adjust it again......the cable snapped so it involves removing the petrol tank and adjusting with a screwdriver.
The engine doesn't like to rev up smoothly and tends to bog down under load when I open the throttle. Suddenly it will come to life and the revs will climb quickly, almost as if it was only firing on one cylinder and then starts to run on two. If I remove the plug cap from the spark plug on either cylinder it runs for a few seconds and then dies, it will not run on just one cylinder.
It has a Motad two into one exhaust rather than the standard Kawasaki single pipes for each cylinder, some people say it gives a flat spot between 4000 and 5000 rpm but my bike isn't running well enough throughout the rev range to be able to tell.
The sender unit to the fuel gauge no longer works although it did work 13 years ago, even then it didn't work very well because it registered empty when it was still 1/3 full, I suspect it has corroded inside.
I will need to treat the tank soon because cleaning out the tank using stones etc to remove the loose rust hasn't stopped rusty material finding its way to the carbs and causing poor running, an inline fuel filter should keep that problem at bay temporarily.
Clearly some further work is still required to bring this old bike back to its former glorious condition!

Lothi · Verfasst am: Di Nov 16, 2010 6:38 am Titel:

Hi Blue Cod

To let the bike run on one cylinder You have to adjust idle revs to >3000 !
Then it will run even with one cylinder.
Easier it will be to unscrew the spark plug, but You have to take care to put the spak plug into the spak plug connector after and to give contact to the chassis/body to the spark; the cdi doesn't like to run without load !

Bogging down under load/dieing when opening the throttle is typically for carbs out of sync and /or blocked jets

Best to clean the jets and to get rid of these gummed/hardened residues is to use acetic acid (vinegar) and a toothbrush ! This "magic bullet" can dissolve residues which even ultrasonic can't!

Also the idle speed system has to be controlled
Especially the small washer for the idle-mixture-controll-screw/pilot screw

As stated on my homepage the bike is very very sensitive to carbs out of sync ! More than an experienced motobike mechanic might expect !
_________________
Grüsse

Lothi tach

Blue cod · Verfasst am: Di Nov 16, 2010 12:19 pm Titel:

I'll try taking the bike on a longer ride today to see if it clears anything from the carbs. Fuel has some redex in it, so I hope that will help.
Already stripped the carbs down several times to clean them.
Boiled the dismantled carbs in a 10% solution of lemon juice(similar to using vinegar as it's a weak acid) last week and used carb cleaning spray afterwards.
Jets were clear, nylon fishing line pushed through the tiny holes. A few weeks back all the jets were definitely blocked with gummed fuel and rust and the bike would not run at all.
The vinegar trick looks to clean them really well as my float bowls are still lightly discoloured compared to yours.
I have replaced both the washers and o-ring seals on the air screw, idle is considerably improved but as I mentioned the pick up on opening the throttle isn't so good despite those settings not being changed recently.
My mechanic is out of practice with carbs too as all the bikes he works on these now have fuel injection(mainly modern racing bikes).
Each time the carbs are cleaned the bike seems to run slightly differently!
If the longer run doesn't cure the running problems I'll try out your other recommendations.
Thanks again for your input and I'll keep you updated on my progress.

Blue cod · Verfasst am: Mi Nov 17, 2010 7:34 pm Titel:

Tickover(Idle) and motorway speeds seem to be okay now but anything inbetween is difficult. Ride is very jerky and little power until main jet takes over, makes it difficult to ride in traffic. 3000-7000 rpm being the problematic region of the rev range.
As the jets are clean, presumably it's the internal fine drillings in the carb body which are partly blocked and are affecting the pilot system. It feels like it is running out of petrol but clearly isn't because it pulls strongly on full throttle. It runs well at 70mph(110kph) around 7000rpm and has a maximum speed of 85mph(130kph) at around 8500rpm in sixth gear. I believe the 305 should have a top speed around 100mph but if it pulls well around 70mph I'm happy with that because that's the maximum legal speed allowed in the UK. The jerky power delivery in the mid range 30-50mph(50-80kph) is a real problem though.
How would you get the vinegar into these drillings, would you have to steep the whole carb in a couple of litres of vinegar?
Rear shock absorber has started leaking oil now, grrr!

Lothi · Verfasst am: Fr Nov 19, 2010 6:51 pm Titel:

Hi Blue Cod

Your symptoms could be carbs or ignition
So I will poste 2 answers

Part one

Carbs:

In the first third of raising throttle only the bypass-system (idle-speed system) is runing ! And the gpz305 is also very very sensitive to carbs out of sync !
Main jet begins to start at 1/3 throttle and takes over at more than 1/2 thottle !
If the idlespeed-system is not working properly You will also encounter higher fuel-consumption and problems You describe seem typically for that.
If the carbs are awesome out of sync You will have different
colour of spark electrodes on both cylinder !

If the jets were blocked by gum best is to use vinegar. I don't no why, but this pits the gum/rust etc.
It is not the acid which does the work ! In the past I also tried lemmon-juice, but that didn't liqudate these residues bur only the rust !
Take a plastic-bowl enough to fit the carb-body, fill in water with some vinegar-essence or buy the cheapest bottle vinegar You can find. Usually it is 2-5% acid. Soak parts (jets; carb-body etc.) well for about 5 Minutes and take a toothbrush or something similar to brush it while in the plastic-bowl. If it is clean use fresh water to rinse the acid.
Done Smile

Maybe You need an air-comrpessor to blow the jets and the very small /"microscopic" drills (like these) in the carb-body and in the jets.
The vinegar does You a favourite there: It will pit the rust *and* embrittle the gum, so it is easy to brush it or to blow it away after !
This does not work with lemon-acid: it only dissolves the rust, not the gum-rubbish.

Make a rough synchronisation as described here: http://www.gpz-305.de/English/Tips/Carbs.html

Vaccum-gauge selfmade: with transparent plastic-tube and motor-oil:
http://www.lothi.org/forum/gpz-305/album_page.php?pic_id=178
Synchronisation must be adjusted on higher revs (~3000), not on idle-speed !
_________________
Grüsse

Lothi tach

Lothi · Verfasst am: Fr Nov 19, 2010 6:58 pm Titel: Ignition

Part two:

Ignition

Same symptoms will arise if the ignition system does not shift the igntion-point.
There are 2 pickups, one for left, one for right cylinder
Also there is a loading-coil for the CDI which is not one single coil: there are 2 coils sticked togehther in the middle: one for charging the Capacitor and one marking the ignition-point for high revs (>3000; advance ignition; ~45°)
The pickups signal only ignition-point for idle speed (~12°)

So if one coil isn't working well You will also have the problems You have told.

To do a favour for Your igintion/CDI and Your electric:
Buy white vasline, best buy it from a pharmacy !( - for human use - it must be acid-free )
unplug all connectors at the CDI and on the frame side (way down to generator)
If copper-oxyde: brush it with vaseline !
Please don't use Contact-spray in any way; it will worse the situation after some days ! Surely !
Nevertheless put some vaseline on all terminators before You plug it together, as future conservation : white vaseline stops water and therefore any corrosion; and white vsaeline ist classical "terminal grease"and also used in classical telephone systems and in switches (e.g. light switch)

If unplugged You can meassure the coil-resistances:
1) at generator-side they should not have any contact to the frame, under no circumstances.
2) left and right pickup-coils should roughly have equal resistance (+/- 20% is ok)
3) the loading-coils for the CDI are not equal ! -> one is for high revs, the other is for idle-speed; but they are fixed together in the middle:
black-red (for charging the capacitor) ~ 200-400 Ohm
white-red (for high revs) ~ 2 -4 Ohm
No contact to the frame !
_________________
Grüsse

Lothi tach

Blue cod · Anmeldungsdatum: 15.11.2010 Beiträge: 14 Wohnort: England Status: **Offline**

I'm pretty sure my bikes running problems are carb related. Bike no longer conks out and the tickover can be set to a steady 1500rpm.
When I am riding at less than 6000rpm the bike doesn't feel smooth but acts a bit like it is running out of petrol, applying the choke in the lower rev range improves the way it pulls.
I'm going to change the carbs again, just rebuilt some after soaking them in vinegar overnight.
Hopefully it will run properly at last.....the carbs have been on and off the bike at least 10 times now!
Also replaced the fuel gauge sender unit as it reads empty even when the tank is full.

Lothi · Verfasst am: So Nov 28, 2010 6:36 am Titel:

Hi Blue Cod

If You are sure the carb is clean, float-gauge-level is ok and the symptoms are only between a fixed range of revs I would guess 2 other possibilities:

First could be air leak at the air intake manifold (rubber might be embrittled)
You can check this by spraying some aerosol start aid
(or a piece of cloth soaked in gasoline) at the air intake manifold (engine-side)

Special to the gpz with the electronic security which stops the engine when strating with unfolded side-stand (most european countries) :
In rare cases it could be the side-stand switch which began to rattle inbetween a special range of revs !
To check this You have to bypass the whole electric which detects side-stnd, clutch-lever and neutral-gear-lamp:
On CDI You have a seperate brown cable. This must be fixed to ground on CDI-side ("shortcut") permanently. This way the system is always in "running state".
If the symptoms vanish after it is probably the side-stand-switch.
(folded it must have peramently contact)

In both cases applying the choke changes vibration (rattling side-stand-switch) and enriches the mixture in case of an air leak
_________________
Grüsse

Lothi tach

Blue cod · Verfasst am: So Nov 28, 2010 9:42 pm Titel:

You will be pleased to know the latest treatment of the carb cleaning fiasco has cured the running problems. The carbs will probably need setting up with vacuum gauges etc to get the maximum performance out of the rebuilt engine.
After the vinegar soak I rinsed the carbs under the tap and then put them in the dishwasher with a little washing up liquid.
Then I rinsed vinegar through all the drillings again using a pipette. scrubbed the carb body with a nylon brush and washing up liquid as the carbs looked cleaner for going in the dishwasher.
Put the carbs in the dishwasher again and when nearly dry squirted carb cleaner(from an aerosol can) into all the drillings, carbs now look almost spotless!
Lubricated all the springs and moving parts with copper lube(grease) and/or ptfe lubricant, then put them back on the bike.
The vinegar must have done the trick as my mechanic had suggested throwing the carbs away, but the bike is running better now than at any time since I bought it 15 years ago.
Another mechanic by passed the CDI unit problems with the switches etc shortly after I bought the bike, the running problems were mainly due to blocked carbs even back then...which is how I came to have 2 sets of carbs(which I've been swapping over and over again over the past couple of months).
The wiring was pretty dodgy 15 years ago so I ended up cleaning as many of the connections as I could and applied vaseline as you suggest. I still need to do the ignition switch connections though.

Lothi · Verfasst am: Mo Nov 29, 2010 8:26 pm Titel:

Hi Blue cod

The old fashioned vinegear can do what modern and toxic chemical high-tech failed happy

I haven't belived it when someone told me this in the past, but practise convinced me.
Your mechanics will look suprised biggrin

_________________
Grüsse

Lothi tach

Blue cod · Verfasst am: Sa Dez 11, 2010 9:59 pm Titel:

I didn't believe the vinegar treatment either but am now a believer!
Now I have begun having starting problems, once bike is warmed up it runs reasonably well.
I noticed the right side carb leaked a little fuel from the overflow pipe but doesn't do it all the time.
When trying to start the bike it refuses, eventually starts without choke followed by quick application of the choke to keep it running.
Is it likely to be the float height or float needle valve which isn't sealing which causes this problem?
Once started it needs to run for about a minute before I can ride it. From cold it takes a few minutes before the right exhaust header pipe begins to warm up and then I can reduce the choke.
I'm now wondering if it's an electrical problem as well, because the feed wire to the right coil snapped a few weeks ago and the wire seemed brittle and had a dull copper colour rather than shiny copper as in new wire.

Lothi · Verfasst am: So Dez 12, 2010 8:57 am Titel:

Hi Blue cod

Try to controll fuel-level in the carbs:

Take a transparent tube, fit it on the drain (exchange it temporarily with black one) and bow it up ("U"-shape) to use it as an old-fashioned gauge.
Open the drain-screw and check in the tube if the fuel-level ist equal on both sides and sligthly below the carb-gasket, approx. 1-3 mm.

When You start the engine it is common for this bike that it cannot start without choke. If it can start for some seconds and needs some artistical performance after on the choke, but cuts off it the choke is steadily on (which it should be for 1-2 minutes) it could be due to several reasons.

Try to check if the engine runs well on both cylinder if warmed up:

Adust idle-speed to 3000rpm temporarily (black knurrled screw)
Unplug one spark-connector, plug a spare-spark into the connector now and fix it to the chassis (this way the CDI has its load)
Start engine again, it should run with one cylinder - with low revs, but it should run.
Try to accelerate slowly; this should also work.
Now change to the other cylinder; behaviour should be equal

Assumed that the carbs are synchronised well and fuel-level is o.k. and You have already exchanged the sparks (new ones) next to check could be:

Too low compression (below 6,5bar)
Problems with ignition
In some rare cases it is a blocked exhaust (rust-pieces inside)

If You suppose ignition-problems it is not easy to figure out what is wrong.
Good is to check the "face" of the spark.
You can also try to swap the pickups.
Easier would be to measure the coils from the CDI-connector-side (while rattling a litte at the wires/connectors way down to the generator).
Other possibilitiy can be problems with the ignition-coil; these You can swap and watch if the problem swaps also to the other cylinder.
Also it could be sometimes the side-stand-switch or other contact which reacts on vibration/shaking. But You have told that on Your bike a mechanical has already made this inactiv (brown cable to ground)
If you do Your "start-procedere" You can also check if the exhaust heats equal (hand at the outlet) or "sniff" on both exhausts if one smells like fresh gasoline.

If You are new to this bike: It is usual that you need to engage the choke ("on") to start the bike and you need not to disengage it before the bike has warmed up (1-2 minutes). If You do the engine cuts off. This is typical for this bike, in contrast to most other bikes which need the choke only for the starting-process
It is a drawback for the low fuel-consumption of the bike.
And also a source of typical accidents for newbies: while driving out with choke engaged the bike speeds up suddenly which tends to end at the garden-fence for the unprepared biker Wink

_________________
Grüsse

Lothi tach

Blue cod · Verfasst am: Do Nov 03, 2011 1:11 am Titel:

The bike repair hasn't been a success, the starting problems got worse and I couldn't rely on it. Also it started leaking fuel and it was impossible to adjust float height. So very few miles were done on it last year and this.
So far the carburetor problems were identified by a carb and bike tuning expert, he has managed to create a set of working carbs from both sets I had plus some new components. New float valve seats dealt with the leaking fuel, but it's a trade secret how he changed them as they are not a screw fit and don't pull out! He also had to modify the way the float valve tabs worked as they were causing the float not to shut off properly.
As my bike had been overbored, he had to adjust the needle holder to stop the bike running lean on fuel. He's managed to tune it properly using various meters and the rolling road(dyno). Although he spent a lot of time getting it to work properly, he says it now starts and runs very well, probably better than when it was new and he expects it to last a long time.
A replacement vacuum style tap has been put on the tank to replace the old gravity fed one.
I may end up with a different fuel tank because even having used Biorust on it (which made the tank look like new inside, shiny metal appearance amazed me) and installed an inline filter, red rust coloured powder still accumulated in the float bowls.
Once the new shock absorber is on the machine it should be road worthy again.
I should get it back just in time for winter, with any luck I'll get some long rides in before we get snow again!