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81 Kz750LT (n2) runs very erratic on cold start.
- ironslave
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If I try to ride to soon it sputters and backfires and runs like a dying horse. Once it warms up though it runs great without choke except for a flux in RPM's at idle.
anyone have some suggestions?
1981 KZ750 LTD
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- 650ed
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1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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- Motor Head
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- FIX UP YOUR BIKE RIGHT AND CHEAP
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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...
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- JR
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I'm not totally sur of the differences/similarities between your 750 and my 1980 750/4 E1.
I start on full choke and after maybe 20 seconds warm up the bike will seem to stumble. at this point I reduce the choke a tad and it smooths and sound better. Put on helmet and zip up jacket and reduce choke a bit more. I have been told it's wrong but I dont wait for the bike to totally warm, I just go with the choke at about a 1/4. At this point the last part of choke travel is just a high idle and the actual choke butterflies are fully horizontal. At the first stop light I'll usually turnt he choke off altogether. When fully warm I have the idle set at maybe 1200 rpm. I like it like that and I think the manual says to have ith in this area anyway. The first part of your post sounds perfectly normal. Your second paragraph is definitely not normal. A good examination of the carbs or a carb clean or synch may help.
One last thought - do you have that anti smog tubing from head to airbox that was fitted to US bikes?
1980 kz750E1, Delkevic exhaust
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- ironslave
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Not sure what this is. I have a tube for the crankcase vent and another tube that runs up to the frame under the gas tank. I assumed it was part of the vacuume system. should I remove that?JR wrote: One last thought - do you have that anti smog tubing from head to airbox that was fitted to US bikes?
JR I can tell you the 1980 and the 1981 engines are actually different. the 1981 kz750N engine is redesigned based off of the 650. I can't remember what exactly the differences were though.
Ok, I took compressed air and blew out all of the circuits when I got the bike. I will try removing the idle screws and blowing them out from there.
UPDATE: I am deffinately thinking it is running lean as today on my way to work the bike lost power on acceleration intermitantly for a few minutes. It now idles irratically as well. I am going to hope I make it home with out any issues. no backfires though.
If I find a cracked boot are there any suggestions on temp fixes until I get a new one in?
also, when I got the bike the petcock vacuume feeder was sticking and it was flooding the carbs until it was used a bit but It seems to work fine now. could it be sticking and not feeding enough fuel into the carbs? only getting enough fuel ro run after a little sit time.
1981 KZ750 LTD
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- JR
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Patton has posted a nice schematic. See if you can find it
edit> found an example. Click here kzrider.com/forum/3-carburetor/531216-79...ve-carby-info#531826
and scroll down
1980 kz750E1, Delkevic exhaust
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1973 Z1
KZ900 LTD
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- ironslave
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Anyway. I think my problem may indeed be electrical. whats the best way to check for intermittent spark? I think the bike is intermittently misfiring. I am gong to go get some spark plugs later.
1981 KZ750 LTD
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- bountyhunter
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Sounds like what happens when rusty junk from the gas tank gets into a main jet.ironslave wrote: UPDATE: I am deffinately thinking it is running lean as today on my way to work the bike lost power on acceleration intermitantly for a few minutes. It now idles irratically as well.
Has the tank and fuel system been cleaned?
Inline filters installed?
1979 KZ-750 Twin
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Original coils? Old coils will often misfire after warm up. Sometimes they just misfire all the time.ironslave wrote:
Anyway. I think my problem may indeed be electrical. whats the best way to check for intermittent spark? I think the bike is intermittently misfiring. I am gong to go get some spark plugs later.
1979 KZ-750 Twin
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- ironslave
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no inline filter, tank is dirty but the petcock filter looks great.. I will flush the tank tomorrow.
I thought about how this all works out, I decided to simulate riding and rock the bike on its center stand while it was running. It decided it that idle should raise almost 1000RPM's if I rocked it for a few seconds. I would snap the throttle and it would drop 4-500 rpm and then after I turn it off and start it idle returned to normal.
The idle is stable after it warms up. it ran for like 30 minutes just sitting there at idle with no problems.
1981 KZ750 LTD
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- 650ed
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ironslave wrote: Coils, thats what I was thinking too. It has a stock coil and an aftermarket coil. the aftermarket coil is much stronger.
no inline filter, tank is dirty but the petcock filter looks great.. I will flush the tank tomorrow.
I thought about how this all works out, I decided to simulate riding and rock the bike on its center stand while it was running. It decided it that idle should raise almost 1000RPM's if I rocked it for a few seconds. I would snap the throttle and it would drop 4-500 rpm and then after I turn it off and start it idle returned to normal.
The idle is stable after it warms up. it ran for like 30 minutes just sitting there at idle with no problems.
I hope you had a fan blowing on it. These bikes have air cooled engines and need air flowing over the cooling fins or they will over heat. Letting a KZ sit and idle for 30 minutes is not a good thing to do. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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