Put in new jets...bike won't start =(
- JonGPZ750
-
Topic Author
- Offline
- User
- Posts: 8
- Thanks: 0
Re: Put in new jets...bike won't start =(
12 Jan 2015 16:40
Thanks everyone for all the advice!
heres where I stand now, the bike starts with I have 117.5 main jets and 37.5 pilots however when the bike warms up it high revs a lot just idling...what can I do to lower the revs also I back out the idle screws still high rev.
thanks again everyone
heres where I stand now, the bike starts with I have 117.5 main jets and 37.5 pilots however when the bike warms up it high revs a lot just idling...what can I do to lower the revs also I back out the idle screws still high rev.
thanks again everyone
Please Log in or Create an account to join the conversation.
- Tyrell Corp
-
- Offline
- User
- "You were made as well as we could make you"
- Posts: 1650
- Thanks: 261
Re: Put in new jets...bike won't start =(
12 Jan 2015 17:59 - 12 Jan 2015 18:02
These GPz were always cold-blooded, and it takes a mile before they will run cleanly off choke.
The chokes on full often race a cold engine too high, if you open the throttle on a cold start it bypasses the 'choke' (enrichment circuit' on a CV carb).
Maybe you need to set the idle by the adjuster when it is hot firstly, then balance the carbs. If youcan't balance them then bench synch them with a drill bit. Check your fuel height too. The 'idle' screws are actually your pilot airscrews on top of the covers, generally around 1.5 -2.5 turns out.
I like pod filters, but they can take some setting up. More info on what jetting you started and finished at might be informative. Unless you are way too big, I suspect maybe something like fuel height, needle position or carb balance has been unintentionally altered when rejetting.
The chokes on full often race a cold engine too high, if you open the throttle on a cold start it bypasses the 'choke' (enrichment circuit' on a CV carb).
Maybe you need to set the idle by the adjuster when it is hot firstly, then balance the carbs. If youcan't balance them then bench synch them with a drill bit. Check your fuel height too. The 'idle' screws are actually your pilot airscrews on top of the covers, generally around 1.5 -2.5 turns out.
I like pod filters, but they can take some setting up. More info on what jetting you started and finished at might be informative. Unless you are way too big, I suspect maybe something like fuel height, needle position or carb balance has been unintentionally altered when rejetting.
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces
Last edit: 12 Jan 2015 18:02 by Tyrell Corp.
The following user(s) said Thank You: JonGPZ750
Please Log in or Create an account to join the conversation.
- JonGPZ750
-
Topic Author
- Offline
- User
- Posts: 8
- Thanks: 0
Re: Put in new jets...bike won't start =(
12 Jan 2015 19:52
Alright so here are the changes I have made its not much because I have gone back and forth.
Airbox before Now pod filters
main jet before 115 now 117.5
Pilot jet 37.5... I do have 40
new Sparkplugs
Bike Runs and idles at like 5rpm
Airbox before Now pod filters
main jet before 115 now 117.5
Pilot jet 37.5... I do have 40
new Sparkplugs
Bike Runs and idles at like 5rpm

Please Log in or Create an account to join the conversation.
- Tyrell Corp
-
- Offline
- User
- "You were made as well as we could make you"
- Posts: 1650
- Thanks: 261
Re: Put in new jets...bike won't start =(
13 Jan 2015 10:18
5k rpm off the choke I think would take more air/fuel than the idle circuit can provide - your throttle plates should all be about 99 percent closed on idle. Even if your throttle grip is shut, if your throttles are partly open too far then the 'choke' enrichment circuit is bypassed.
Adjust this idle with the adjuster knob on the carbs when hot, if the carbs are far out of balance you won't gt a smooth idle.
Adjust this idle with the adjuster knob on the carbs when hot, if the carbs are far out of balance you won't gt a smooth idle.
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces
Please Log in or Create an account to join the conversation.
- bountyhunter
-
- Offline
- User
- Posts: 7246
- Thanks: 338
Re: Put in new jets...bike won't start =(
13 Jan 2015 12:37That is the classic symptom of a vacuum leak.JonGPZ750 wrote: Bike Runs and idles at like 5rpm
1979 KZ-750 Twin
Please Log in or Create an account to join the conversation.
- tachrev
-
- Offline
- User
- Rubber Side Goes Down
- Posts: 343
- Thanks: 11
Re: Put in new jets...bike won't start =(
13 Jan 2015 13:00bountyhunter wrote:That is the classic symptom of a vacuum leak.JonGPZ750 wrote: Bike Runs and idles at like 5rpm
I second this. Sounds like you have a leak.
1977 Kawasaki KZ1000 : Street/Strip
Build Thread
Build Thread
Please Log in or Create an account to join the conversation.
- Tyrell Corp
-
- Offline
- User
- "You were made as well as we could make you"
- Posts: 1650
- Thanks: 261
Re: Put in new jets...bike won't start =(
13 Jan 2015 17:56
..also bypassing the enrichment circuit hence the starting and hot idle problems.
When they are leaking just a bit they won't idle evenly. Also cracks in the rubber manifolds from heat and aging aren't always apparent until you take them off and squeeze them.
When they are leaking just a bit they won't idle evenly. Also cracks in the rubber manifolds from heat and aging aren't always apparent until you take them off and squeeze them.
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces
Please Log in or Create an account to join the conversation.
- JonGPZ750
-
Topic Author
- Offline
- User
- Posts: 8
- Thanks: 0
Re: Put in new jets...bike won't start =(
18 Jun 2015 13:36
Sorry for the late update, been busy.
I Got It up and running !
Everyone's advice was pretty much all right. It was a combination of getting the right jet combination.
Finding and eliminating vacuum leaks. Turns out all 4 of the Corroborator boots when completely destroyed.
Thanks all
I Got It up and running !

Finding and eliminating vacuum leaks. Turns out all 4 of the Corroborator boots when completely destroyed.
Thanks all
Please Log in or Create an account to join the conversation.
- Randombeat
-
- Offline
- User
- 0 to 100 real quick...
- Posts: 274
- Thanks: 23
Re: Put in new jets...bike won't start =(
20 Jun 2015 07:29
So what size jets did you end up with?
1980 KZ750H LTD-- pods-- vance & hines 4-1 --speedo/tach/blinker/switch deletes -- brat style
Please Log in or Create an account to join the conversation.