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Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 19 Mar 2017 08:55 #757125

  • gordone
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KZ650-D4 w 81 750-4 engine. VM24 carburetors w 125 main jets, 25 pilot jets, jet needle clipped at the X groove. air screws 1,5 turns out from seated. K&N individual filters, properly cleaned w K&N cleaner & properly oiled. 4-1 exhaust system.
(note: I would underline or highlight KZ750-4 engine as I've done above).

1. Valve Adjusment has been done.
2. The carbs have been thoroughly cleaned.

I started up the bike yesterday after all the work above has been performed.
I have not tunned carbs before, so I started up the bike without any problem, let it warm up.
I tried to turn on air screw to find the posistion where the RPM is highest, these was not easy, but I think I found something.

The engine goes smoth on idle, and when you give throttle in natural it follow the throotle as it should.
When you run the bike it`s going quite good on 1-4k RPM, over that it start to cheating, if I`m increase the RPM slowley will it build up the RPM quite okay, but if you give full throotle it`s "cheating" almost like it not has started properly / bad timing.. wrom wrom.. and then it comes... but not with full HK?

Today i cleaned the spark plugs, started the engine and let it run to it was warm and then took it to a test run in a hill, where I was giving full throttle in 2 or 3 gear, the RPM was going up to around 6K, and was stable, but it was not going further above around 6K... but the engine was going constant without any cheating. I shutoff the engine with the kill switch whill I had 6K RPM, picture of the spark plugs can be found here:
temp.dynamitt.net/div/MC/carb_tuning/

I have used alot of time on the carbs / valves etc.. so I`m really keen to get its working correct now :)

I`m grateful for you taking time to reading these, if you need some more information from me don`t hesitate to contact me.
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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Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 19 Mar 2017 18:44 #757176

  • baldy110
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Your way to rich on your jetting. Go to 112.5 on the main jets and 17.5 on the pilot jets. Put the needle clip in the middle slot. And use mikuni jets not the ones that come in those cheap ebay kits. That should get you pretty close.

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Last edit: by baldy110.

Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 19 Mar 2017 19:41 #757182

  • Nessism
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Do you have real K&N branded filters? If so that's good. Those cheap emgo cheepie filters are not made like K&N's and they are not supposed to be oiled. In one of your other threads you provided photos of the filters and they didn't look like K&N's, but I could be wrong (and hope I am).
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Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 07:35 #757208

  • KZB2 650
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Try pulling off the pods for a quick ride...... That will tell you if the pods are a problem..... I ran 17.5s and 117.5s, clips on the 5th with open 24s and a baffled header for years and it ran exc. Went to 112.5s after getting the pods like Baldy says then back to the 117.5s after the cams and bore job. I can't believe your 810 Baldy runs so good with the clips in the middle on the needles.... (don't get me wrong I trust you) its just that the 4th clip (one step richer) is stock on the 650 in both manuals and info on the net.

Have you set the pilot jets on the bottom of the bowls to 1 or 1 and a 1/8th turn out yet? Not sure if you needed to start this new thread since you have the other one going but maybe you'll get a couple new idea's.
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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Last edit: by KZB2 650.

Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 11:28 #757228

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baldy110 wrote: Your way to rich on your jetting. Go to 112.5 on the main jets and 17.5 on the pilot jets. Put the needle clip in the middle slot. And use mikuni jets not the ones that come in those cheap ebay kits. That should get you pretty close.


Thank you for your feeback, I have a understanding you are pretty sure these is the problem ?
Where will you recommend to by the jets on internet?
When I purchase, shall I by some extra also one step down og up ? example?
So I have some extra if I need to adjust from what you are saying I can test with?

Thank you.
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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Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 11:31 #757230

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Nessism wrote: Do you have real K&N branded filters? If so that's good. Those cheap emgo cheepie filters are not made like K&N's and they are not supposed to be oiled. In one of your other threads you provided photos of the filters and they didn't look like K&N's, but I could be wrong (and hope I am).


It is stand K&N on the end of the filteres? Can it be China, fake ?? I don`t thing so?
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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Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 11:36 #757231

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KZB2 650 wrote: Try pulling off the pods for a quick ride...... That will tell you if the pods are a problem..... I ran 17.5s and 117.5s, clips on the 5th with open 24s and a baffled header for years and it ran exc. Went to 112.5s after getting the pods like Baldy says then back to the 117.5s after the cams and bore job. I can't believe your 810 Baldy runs so good with the clips in the middle on the needles.... (don't get me wrong I trust you) its just that the 4th clip (one step richer) is stock on the 650 in both manuals and info on the net.

Have you set the pilot jets on the bottom of the bowls to 1 or 1 and a 1/8th turn out yet? Not sure if you needed to start this new thread since you have the other one going but maybe you'll get a couple new idea's.


Thank you for sharing these information so you have same engine and carbs?
I will test without pots and also order new jets. So you also agree with Blady, shall i order more jets when I first do it?

I found a guide for findings the correct air scew posistion, turn it out 1 1/4 and find the place where you have highest RPM,
I found it realy hard, when it have screw to buttom I can hear the engine don`t like it and when I have screw 1 + someting I can hear the sound is better, but the RPM is not increase alot. I took a video from it:
temp.dynamitt.net/div/MC/carb_tuning/IMG_3698.MOV

I started these new thread to be clean and only focus on these problem.
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.

Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 13:21 #757240

  • baldy110
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KZB2 650 wrote: Try pulling off the pods for a quick ride...... That will tell you if the pods are a problem..... I ran 17.5s and 117.5s, clips on the 5th with open 24s and a baffled header for years and it ran exc. Went to 112.5s after getting the pods like Baldy says then back to the 117.5s after the cams and bore job. I can't believe your 810 Baldy runs so good with the clips in the middle on the needles.... (don't get me wrong I trust you) its just that the 4th clip (one step richer) is stock on the 650 in both manuals and info on the net.

Have you set the pilot jets on the bottom of the bowls to 1 or 1 and a 1/8th turn out yet? Not sure if you needed to start this new thread since you have the other one going but maybe you'll get a couple new idea's.


My needle clips are in the middle but with a shim under them and I live at 4000 feet so it makes a small difference. I was just trying to get him in the ball park.
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Last edit: by baldy110.

Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 13:21 #757241

  • Nessism
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Dennis Kirk is a good place to get REAL Mikuni jets...www.denniskirk.com/mikuni/1.pg

I'd target the jetting range highlighted by the guys above. Something in the range of 17.5/115.

One other thing to check...

If those carbs have pilot fuel screws on the underneath side remove them and check the tips. They should be sharp and pointy. Sometimes guys turn them in too hard and the tip gets wedged into the carb body and then they break off.
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Last edit: by Nessism.

Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 15:39 #757247

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Nessism wrote: Dennis Kirk is a good place to get REAL Mikuni jets...www.denniskirk.com/mikuni/1.pg

I'd target the jetting range highlighted by the guys above. Something in the range of 17.5/115.

One other thing to check...

If those carbs have pilot fuel screws on the underneath side remove them and check the tips. They should be sharp and pointy. Sometimes guys turn them in too hard and the tip gets wedged into the carb body and then they break off.


Can you explain 17,5/115 ? Your idea is that I can adjust the rest with the clips hight on the needle?
So I can adjust around 115 range? Since baldy have good experience with 17,5/112,5 and KZB2 650 with 17,5/117,5 ?

I found jets on the webpage, have I found correct? I can see you can choice size on the page, so I only need to change size when I fully understand from you guys what I shall choice. See attached picture of the jets I have now.

Pilot jet Size 17.5
www.denniskirk.com/ebc/rd-vm22-210-pilot...96.prd/173396175.sku

Main Jet 112,5
www.denniskirk.com/ebc/rd-precision-miku...9.prd/1723991125.sku

Shall I purchase 17,5 / 112,5 and 115 ?

There are no more screws underneath I think, I haven`t taken pictures, but I think these was the only one.

What do you think everybody ? is these the problem the jets? It will be good possibilities these will solve the problem?
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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Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 20 Mar 2017 16:09 #757252

  • Nessism
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Looks like you are getting close. It won't hurt to have a few different options in terms of those main jets.

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Help needed. 81 KZ650-D4 w 81 KZ750-4 engine & VM2 21 Mar 2017 04:43 #757286

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Nessism wrote: Looks like you are getting close. It won't hurt to have a few different options in terms of those main jets.


The jets is cheap, so I can ordere more then one, I`m living in Norway, so I will use some more money instead of ordering many times :) heeh
What sizes shall I order do you think or others?
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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