KZ750H Restoration
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Re: KZ750H Restoration
09 May 2020 12:03
Sounds more like a little valve ticking but nothing to worry about. I would do some more break in miles first ( 500 km ) before i would put my hands on the engine.
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Re: KZ750H Restoration
09 May 2020 14:30
Engine noise sounds normal. Some primary chain and clutch chatter is all.
Did you vacuum sync the carbs? If not, it will improve the idle stability.
Did you vacuum sync the carbs? If not, it will improve the idle stability.
Ed
Carb O-ring Kits : www.kzrider.com/forum/3-carburetor/61807...-o-ring-kits?start=0
www.kzrider.com/forum/faq-wiki/618026-new-owner-things-to-know
1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
Carb O-ring Kits : www.kzrider.com/forum/3-carburetor/61807...-o-ring-kits?start=0
www.kzrider.com/forum/faq-wiki/618026-new-owner-things-to-know
1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
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Re: KZ750H Restoration
09 May 2020 14:44
Thanks guys, good to hear
This is the first bike (or vehicle for that matter) that I have worked on with carbs. It's also by far the oldest thing I've worked on. So I'm a bit unsure on what's 'normal'.
I have vacuum synced the carbs, but not since I put the new coils on - didn't think it would make any difference. Thinking about it now, there may be slight variance with all the cylinders firing properly (due to more consistent forces on the crank). Will check it again when I replace the fuel line next week (someone cut the line a bit too short... :whistle: ).

I have vacuum synced the carbs, but not since I put the new coils on - didn't think it would make any difference. Thinking about it now, there may be slight variance with all the cylinders firing properly (due to more consistent forces on the crank). Will check it again when I replace the fuel line next week (someone cut the line a bit too short... :whistle: ).
KZ1000 Restomod (
www.kzrider.com/forum/11-projects/614517-1977-kz1000-restomod
)
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
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Re: KZ750H Restoration
10 May 2020 10:49 - 10 May 2020 10:50
Had another ride around the block today - trying to get a fix until I can get it out on the road 
A couple of times it felt like the throttle wasn't returning properly. When I got back to the garage I checked and the throttle stuck open when I revved to about 4000rpm. I shut the bike off and tried again and they stuck with the engine off as well. I could see the slack in the throttle cable, so it's the butterflies that are sticking (Keihin CV34 carbs). The return spring is fine - it hurts my finger to hold the throttle open from underneath the carbs. It only seems to happen when the bike is well warmed up - even though the carbs don't warm up that much. It doesn't seem to be at a particular position as it has happened at 2000 and 4000 rpm in neutral. It also isn't consistent, so I don't think it has to do with thermal expansion (although this is the only explanation I have at the moment).
Not really sure how to diagnose this one.

A couple of times it felt like the throttle wasn't returning properly. When I got back to the garage I checked and the throttle stuck open when I revved to about 4000rpm. I shut the bike off and tried again and they stuck with the engine off as well. I could see the slack in the throttle cable, so it's the butterflies that are sticking (Keihin CV34 carbs). The return spring is fine - it hurts my finger to hold the throttle open from underneath the carbs. It only seems to happen when the bike is well warmed up - even though the carbs don't warm up that much. It doesn't seem to be at a particular position as it has happened at 2000 and 4000 rpm in neutral. It also isn't consistent, so I don't think it has to do with thermal expansion (although this is the only explanation I have at the moment).
Not really sure how to diagnose this one.
KZ1000 Restomod (
www.kzrider.com/forum/11-projects/614517-1977-kz1000-restomod
)
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
Last edit: 10 May 2020 10:50 by calum.
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Re: KZ750H Restoration
10 May 2020 11:16
It may require unganging the carbs and doing a thorough cleaning and lube on all the linkage parts. Hope it doesn't have to go that far to solve it.
Retired gearhead
'81 KZ-750 E2
'87 Suzuki Savage 650 Street Tracker (lost in the shop fire)
'81 KZ-750 E2
'87 Suzuki Savage 650 Street Tracker (lost in the shop fire)
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Re: KZ750H Restoration
10 May 2020 11:50
I had another look and the butterflies are binding very slightly, enough to cause the problem. Guess I'll be pulling the carbs again... All things considered, it's not too bad. Considering I've never overhauled carbs before I think I can deal with this as it's been the only real problem so far

KZ1000 Restomod (
www.kzrider.com/forum/11-projects/614517-1977-kz1000-restomod
)
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
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Re: KZ750H Restoration
12 May 2020 12:08 - 12 May 2020 12:09
Pulled the carbs today and checked the throttle shafts. The coating was coming off the number 2 shaft and it was binding quite badly. The return spring would normally close it easily but I think when it warmed up a bit (wouldn't take much) it was causing the throttle to stick.
Replaced the throttle shaft and good to go now.
I did notice that the tip of the drain nipple on two of the float bowls was always wet. They weren't dripping, but if I dried them off then there would be fuel on them again after a while. I checked for leaks but couldn't find any (filled the float bowl with fuel, blocked the overflow tube off with my finger and blew as hard as I could through the drain tube). Is a bit of seepage normal?
Replaced the throttle shaft and good to go now.
I did notice that the tip of the drain nipple on two of the float bowls was always wet. They weren't dripping, but if I dried them off then there would be fuel on them again after a while. I checked for leaks but couldn't find any (filled the float bowl with fuel, blocked the overflow tube off with my finger and blew as hard as I could through the drain tube). Is a bit of seepage normal?
KZ1000 Restomod (
www.kzrider.com/forum/11-projects/614517-1977-kz1000-restomod
)
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
Last edit: 12 May 2020 12:09 by calum.
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Re: KZ750H Restoration
12 May 2020 16:42 - 12 May 2020 16:43
There should be no weapage out the nipple.
Do your float bowls have real overflow tubes or not? If they have the tubes it's quite likely that some are cracked which can cause leaks.
If there is no overflow tubes the wet nipple means the drain screw is leaking.
Do your float bowls have real overflow tubes or not? If they have the tubes it's quite likely that some are cracked which can cause leaks.
If there is no overflow tubes the wet nipple means the drain screw is leaking.
Ed
Carb O-ring Kits : www.kzrider.com/forum/3-carburetor/61807...-o-ring-kits?start=0
www.kzrider.com/forum/faq-wiki/618026-new-owner-things-to-know
1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
Carb O-ring Kits : www.kzrider.com/forum/3-carburetor/61807...-o-ring-kits?start=0
www.kzrider.com/forum/faq-wiki/618026-new-owner-things-to-know
1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
Last edit: 12 May 2020 16:43 by Nessism.
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Re: KZ750H Restoration
12 May 2020 16:47 - 12 May 2020 17:00
They have overflow tubes. I thought they must be cracked, but my pretty primitive testing method didn't seem to work. Is there a better way to test for leaks?
KZ1000 Restomod (
www.kzrider.com/forum/11-projects/614517-1977-kz1000-restomod
)
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
Last edit: 12 May 2020 17:00 by calum.
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Re: KZ750H Restoration
12 May 2020 17:05
Went back and tested one again. Must have had a bit more air in the lungs as I could see bubbles coming out of the overflow tube. They pretty much came out of the whole tube - the whole surface seemed to be porous. Looks like I need to replace them (soldering isn't going to be an option, I'd need to completely cover them.
I'll try to find some brass tubing and see if I can use your repair method.
I'll try to find some brass tubing and see if I can use your repair method.
KZ1000 Restomod (
www.kzrider.com/forum/11-projects/614517-1977-kz1000-restomod
)
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
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Re: KZ750H Restoration
12 May 2020 17:07
I found 1/8" brass tubing at my local hardware store, sold in one foot pieces. His method of replacement worked like a charm.
Retired gearhead
'81 KZ-750 E2
'87 Suzuki Savage 650 Street Tracker (lost in the shop fire)
'81 KZ-750 E2
'87 Suzuki Savage 650 Street Tracker (lost in the shop fire)
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Re: KZ750H Restoration
12 May 2020 17:15
Thanks, should I go slightly bigger or slightly smaller after converting to metric? Assuming slightly larger may mean I don't have to flare them.
KZ1000 Restomod (
www.kzrider.com/forum/11-projects/614517-1977-kz1000-restomod
)
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
1977 KZ1000A1 ( www.kzrider.com/forum/11-projects/616901...-spare-parts-project )
1980 KZ750H ( kzrider.com/forum/11-projects/612054-kz750h-restoration )
2000 BMW F650GS
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