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Start up engine after rebuild 24 Apr 2018 04:59 #782279

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gordone wrote: Thank you for sharing your skills !
Must I wait to 400-500 miles before I start running the engine normal, with stady RPM etc... ?


No. ride the bike normally, just don't sit at constant rpms for too long and risk glazing the bores ..
We are talking sitting for miles at constant revs that will prevent the rings from bedding in fully not a short cruise up the street..
Don't limit your rev range either, no need to keep below 5000 rpm or whatever for 500 miles but don't instantly take it flat out .
All just common sense really..
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
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Start up engine after rebuild 25 Apr 2018 11:57 #782354

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I have got problems....
As you now was I starting up the bike two days ago, all cylinders was running fine and took the bike out for approx. 30 minutes city drive without any issue.
Yesterday was I not using the bike, I was fixing some paint on the exhaust, replace the fuel hose and made some vent house (the two port on the carbs, so water cannot come in).

Today was I tried to start the engine it will not started... I tried a lot with choke and not...

- I checked for spark, and it was spark on all four...
- I took out the plugs and they looked weet...
- Sometimes I can hear it firing some in between... got 1rpm maybe and then die...
- I could feel the pipe was cold on 3, but they other was not hoot either, but I could feel they was warmer.
- I took out the carbs and open-up the carbs up under and used compressed air cleaned the jets etc...
- No differences, will not start....
- I open up the valve cover and measure the valves, 3 was close to 0,08. So I adjusted the valve so all is around 0,13-0,15
- No differences, will not start...
- I took the plugs out and 3 and 4 was wet, but it looks like 1 and 2 was dry....
- I dried to drain the carbs will the fuel switch was in PRI, got gas out from all, but not cylinders 1, nothing...

I think the problem is the carb? But why was the bike running fine when I parked it, and when I start up two days later will not start?

What should I do? Must I take the carb out and clean more, fuel line etc?

Don`t know 100% where to start.

When I got the bike for 1,5 years ago I also had problems, then it started easy, but it was missing power and back firing, then the conclusion was the carb sync was the problem, I mean carb 1 had to lidel openin or something.. so when I open up the carb1 more it start firing good on cylinder 1 also.. and the bike was running fine for the whole summer.

I rebuild-ed the carb when I got the bike.

It was a lot of information here... my head is spinning around :)

I have free these days, so want to be out driving :) was so ready for it, since the engine was running fine two days ago.
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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Start up engine after rebuild 25 Apr 2018 13:03 #782360

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gordone wrote: Yesterday was I not using the bike, I was fixing some paint on the exhaust, replace the fuel hose and made some vent house (the two port on the carbs, so water cannot come in).

- I took the plugs out and 3 and 4 was wet, but it looks like 1 and 2 was dry....
- I dried to drain the carbs will the fuel switch was in PRI, got gas out from all, but not cylinders 1, nothing...




Seems like a problem with either the fuel hose, petcock, or maybe you have debris in the tank which is now blocking up the carbs.

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Last edit: by Nessism.

Start up engine after rebuild 25 Apr 2018 13:35 #782361

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Nessism wrote:

gordone wrote: Yesterday was I not using the bike, I was fixing some paint on the exhaust, replace the fuel hose and made some vent house (the two port on the carbs, so water cannot come in).

I have fuel filter inside the tank, built inn with fuel valve. So I can start the clean process after the tank?

- I took the plugs out and 3 and 4 was wet, but it looks like 1 and 2 was dry....
- I dried to drain the carbs will the fuel switch was in PRI, got gas out from all, but not cylinders 1, nothing...




Seems like a problem with either the fuel hose, petcock, or maybe you have debris in the tank which is now blocking up the carbs.

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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Start up engine after rebuild 26 Apr 2018 06:00 #782396

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Nessism wrote:

gordone wrote: Yesterday was I not using the bike, I was fixing some paint on the exhaust, replace the fuel hose and made some vent house (the two port on the carbs, so water cannot come in).

- I took the plugs out and 3 and 4 was wet, but it looks like 1 and 2 was dry....
- I dried to drain the carbs will the fuel switch was in PRI, got gas out from all, but not cylinders 1, nothing...


Seems like a problem with either the fuel hose, petcock, or maybe you have debris in the tank which is now blocking up the carbs.


Thank you, I see your point.
Some extra information, the gas tank was painted in the winter and it was almost noon gas on it.. So I filled it up with 5 liter of new gas before I started up for the first time.
I think it can be some old paint (dropped into the tank when the old paint was removed) in the tank, because it was not cleaned before I filled up with gas, but I have a petcock with filter:



These filter should avoid anything bad for coming into the carb ? I have not any additional filter.

Today have I done a function test on the petcock, I suck on the vacuum line and the gas comes out as it should.. so the petcock is working, I have also tried to start on "PRI" without any success.

I have also tested with another fuel hose same problem, I used a one you can look through, and the gas goes in for sure...

I took out the carbs today and open up all from the button and I have used carb cleaner and high air pressure for cleaning. The only thing I took out was the air/mix screw and the needle for the flow height. The jets I just sprayed with carb cleaner and high pressure air...

I found the problem why the carb 1 has no gas in the reservoir yesterday, I have mounted the needle wrong yesterday when I tried to clean the carb first time (yesterday).

I installed everything again, and the results is the same....

Some times when I try to start the engine fired up to 1-2 RPM and stay there quite stable for 2-3 seconds and then die....
I have checked the exhau pipe and it`s look to be random what pipe is hoot, normaly 2 og 3 is hot and 4 is cold, but it looks like some times that only 2 has some height..
But I have a feeling its random...

I`m not a expert but if I add these thing together (stop after 2-3 seconds) and the pipe is not hot and its random, it has to be a carb or of fuel problem?

What to-do?

1. Empty the tank and clean it with diesel, use 1 liter diesel and shake the tank, tap of the liter and fill new fresh petrol?
2. Is the carb cleaning I have done not good enough, must I take everything in part and clean?

Or can it be something else I`m not aware of ?
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
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Last edit: by gordone.

Start up engine after rebuild 26 Apr 2018 07:07 #782404

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You might have to clean the tank like you say and hit the carbs with spray once more.......get a inline fuel filter from the bike shop .... the petcock filter stops most but not all (all of us run a second filter). And try new plugs..... and although I dought it has anything to do with the problem un hook the 2 vent lines you installed just for the hell of it.
1978 KZ650 b-2
700cc Wiseco kit 10 to 1.
1980 KZ750 cam, ape springs, stock clutch/ Barnett springs.
Vance and Hines Header w/ comp baffle and Ape pods, Dyna S and green coils, copper wires.
29MM smooth bores W/ 17.5 pilots, 0-6s and 117.5 main
16/42 gearing X ring chain and alum rear JT sprocket.

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Start up engine after rebuild 26 Apr 2018 07:14 #782407

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KZB2 650 wrote: You might have to clean the tank like you say and hit the carbs with spray once more.......get a inline fuel filter from the bike shop .... the petcock filter stops most but not all (all of us run a second filter). And try new plugs..... and although I dought it has anything to do with the problem un hook the 2 vent lines you installed just for the hell of it.


I will try all these, but the plugs are new only used them for det 30minutes drive 3 days ago and under troubleshooting. No reason to replace them?

1. Clean the tank and hoose with diesel?
2. Install sencond filter?
3. Clean the carb?

Try to start up again?
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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Start up engine after rebuild 26 Apr 2018 10:48 #782424

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As much as I hate starter fluid using a shot in each carb will tell you if the problem is the carbs or something else.

Assuming the engine runs for a few seconds on the starter fluid you can be assured the problem is the carbs.

Can't tell you for sure to use diesel in a fuel tank because diesel and gasoline doesn't mix. What I can suggest is to drain the tank and look inside with a flashlight and mirror and see if there is any rust or crud, then take appropriate action as needed.

Regarding cleaning the carbs, I'd remove the pilot jets to see if the holes are plugged. If those carbs use a pilot screw I'd remove those too and blow them out at minimum. Shooting carb spray through the carbs and watching where it comes out is a good way to assure the passages are clean too.

Good luck

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Start up engine after rebuild 26 Apr 2018 11:02 #782425

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Nessism wrote: As much as I hate starter fluid using a shot in each carb will tell you if the problem is the carbs or something else.

Assuming the engine runs for a few seconds on the starter fluid you can be assured the problem is the carbs.

Can't tell you for sure to use diesel in a fuel tank because diesel and gasoline doesn't mix. What I can suggest is to drain the tank and look inside with a flashlight and mirror and see if there is any rust or crud, then take appropriate action as needed.

Regarding cleaning the carbs, I'd remove the pilot jets to see if the holes are plugged. If those carbs use a pilot screw I'd remove those too and blow them out at minimum. Shooting carb spray through the carbs and watching where it comes out is a good way to assure the passages are clean too.

Good luck


Thank you, can I just flush the tank with fresh petrol then?

I will replace the plug and install filter.

Looks to be the same type of filter as pedstock, it was not expensive, hope it do the work?



If these things not help I will try the start gas.
I was thining about it eralier today, but was afraid since engine is new build..,
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
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Start up engine after rebuild 27 Apr 2018 00:39 #782469

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These morning I purchased quick spray for test. I cannot see differense with it. I open up the rhrottle full spray in 1-2 seconds on each carb released the throotle and tried to start... and nothing happens... some times when I trie to start it «starts» goes up to 2k rpm for 2 seconds and then die. When I checked the pipe was 1 and 4 warm, 3 could I feel something, but colder then 1 and 4, the 2 was stone cold...

So no difference in the beviaor with start gas....

I have started thinking has something goes wrong with the new cylinder / pistons rings???

But cannot understand these since my first startup was fine I drive for 30 minutes with any startup problem (tried to start 3-4 times before the tour without any problems) and when I stopped the bike after 30 minutes drive it was running fine....

I tried to replace the plugs with new one today also.

I also checked for spark today, spark on all four...

I will try to clean the tank no anyway, but don’t think it will help.

Your inouts has high value for me! :)

The plan was to drive around these days, have free from work, but tou never know with old bikes :)
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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Last edit: by gordone.

Start up engine after rebuild 27 Apr 2018 05:35 #782477

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I'd say go back to basics and check spark and cam timing.

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Start up engine after rebuild 27 Apr 2018 05:55 #782478

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Good news!

After I had tested with start gas, I purchase a quality gas filter, wanted to just remove all potential problems.

I empty the tank it was around 10-11liter of petrol, I have fill 5l x 2 after the start up so it cannot been much left from before the start up...
I filled new gas approx. 1 liter shaked and empty again.. did the same one more time. Fill up with fresh patrol.

Cleaned the cabs, but these time I took out the jets and also "choke?" the plug you are using when you start up on cold engine, gives some more gass or something?

And then I tired to start up with cleaned tank, petrol filter and clean carbs... and then bike started ! hehe
Some small back firing in the start, but not much.

I adjusted the mixing screw and carb sync.

Took it out from a drive and it goes okay, but not perfect but ok, from 5-6 it is not so smoth... maybe I need to get up in jet size ?

Anyway I will now drive around and get som miles and experience with the bike how it behave and take it from there....

Since I have re shimmed the valve now, I was thinking to not open up the valve cover before around 500 miles when I take ful service,
oil / filter / valve clearness ...

a plan ?

Thank you all for your inputs without you I will noe been able to get it running again.

1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
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Last edit: by gordone.
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