78 kz750b build

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04 Aug 2020 04:57 #832197 by timmdur
Replied by timmdur on topic 78 kz750b build
Thanks for the info!!! I assume that I have the later style? Lucky me I have to return them anyway, as they sent the wrong ones. I originally purchased a set of larger, more ovular filters, so it might solve that issue (pic attatched). If not, do you think it would work to carefully cut a chunk out of the rubber seal, and maybe a bit of foam (not enough to render the filter useless, of course), that obstructs the vacuum passage? Maybe I could even flip them over? The only reason I'm trying to stick with them for now is because I heard someone mention that foamies work MUCH better with cv carbs that pleated filters. Something about how the pleated filters cause intense vacuum fluctuations.
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  • DoctoRot
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  • Oh, the usual... I bowl, I drive around...
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04 Aug 2020 10:12 - 04 Aug 2020 10:13 #832222 by DoctoRot
Replied by DoctoRot on topic 78 kz750b build
It looks like the oval filters have the same flange design as what you have. Cutting into the filter will likely negate the filter, that doesn't seem like a good solution. filter quality has as much to do with the boot design as the filter material. You want the smoothest transition from the boot to the intake as possible, no steps and, under no circumstances, any obstruction of the ports. Many K&N filters have a short venturi built into them which definitely gives them an edge in my book. The only foam filter I have heard good things about is Uni filter but I have never used them, Most people I know who like them are dirt bike riders because apparently they are very easy to clean and oil.
IMHO there are some places where you can cut corners on price. pod filters is not one of them. If you are trying to get this thing going on a budget i would get a stock paper filter and stick with the airbox. Also I would think twice about drilling out jets. I think you are setting yourself up for major carbueration headaches.
Last edit: 04 Aug 2020 10:13 by DoctoRot.

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10 Aug 2020 05:57 - 10 Aug 2020 06:09 #832540 by timmdur
Replied by timmdur on topic 78 kz750b build
Thanks for the words of advice DoctoRot! You're making me nervous about this whole pod filter thing, but ebay wouldn't let me return them even though I received the wrong item (only exchange), so I think I'll give them a try. I have an idea on how I could modify the boots. But I bet I'll give up after a while and build a custom airbox... I just hate the look of the stock one. Also, in regards to drilling the jets, I have an entire spare set, or else I wouldn't try it. The goal isn't to use them permanently, but instead to get an estimate of what sizes I'll need before spending $5 a pop.

I also replaced the starter clutch, and now it engages! But the motor still doesn't turn the engine over. It sounds like it's spinning, but it only turns over the engine when the plugs are removed. I figured the ring gear inside the starter motor was slipping, so I made a new shim and shoved some JB weld in there too, just for good measure. Still nothing. Again, it sounds like it's spinning, but nothing outside of the motor turns (eg. the motor's output shaft). Any ideas as to what this could be?

Lastly, I found a great deal on a set of 1999 r6 forks, so I bought them on a whim. After some inspection, I think I'll be able to easily adapt them, and even run dual discs up front with the stock wheel! I'm thinking of using rear shocks from a zrx1200, unless something better/cheaper can be found.
Last edit: 10 Aug 2020 06:09 by timmdur.

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10 Aug 2020 07:33 #832550 by Skidmark
Replied by Skidmark on topic 78 kz750b build
JB Weld is rarely the correct solution to a problem. Even more so a mechanical one. Just saying... Best of luck solving the issue.

Retired gearhead
'81 KZ-750 E2
'87 Suzuki Savage 650 Street Tracker (lost in the shop fire)

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10 Aug 2020 07:48 - 10 Aug 2020 07:50 #832554 by timmdur
Replied by timmdur on topic 78 kz750b build
I completely agree in most situations, however this was one where the use was warranted. The reason the ring gear slips is to prevent the engine damaging the starter motor if it kicks back. The shim holding the ring gear in place was worn enough that the gear could slip with minimal force applied, essentially allowing the entire starter motor to rotate around the output shaft if met with enough resistance (or so I thought). My goal was to seat the ring gear in place as firmly as possible, while still allowing a large, sudden impact to break it free. A little JB weld packed into an empty shim slot, contacting a mirror-smooth ring gear was my best bet. I did NOT want to begin by dropping $200 on a new starter motor, and I doubt that my shim would hold it in place on its own. If you would like me to, I can post some pics later detailing my beautiful craftsmanship! :laugh:

In all seriousness, thanks for the concern. I understand that generally JB weld is not the answer, but in this case it was my best bet.

I'm actually looking at a new engine, complete with carbs and starter, near me for a REALLY good deal. No more info, though, or someone might snatch it up! :P
Last edit: 10 Aug 2020 07:50 by timmdur.

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10 Aug 2020 09:31 - 10 Aug 2020 09:37 #832561 by Saablord
Replied by Saablord on topic 78 kz750b build

Kaylinator wrote:

timmdur wrote: ! Once I reinstalled the (slightly broken, not synchronized) carburetors, I kicked it over about 1,000,000 times, then took a break to order a new starter clutch... :laugh: But on the millionth-and-first kick it started!!


Getting mine going after 30 years, I kept the truck on the bike battery while using the electronic starter and throwing starting fluid at the carbs. Still took probably at least 20 minutes for it to run. Starts beautifully now.

:laugh: i did the same thing with a 650!

It'll be easier if you use the stock airbox at first just so you're not chasing pod issues when its actually something else.

Also, if you do use cheap pods, just cut out the flange with an xacto knife. typically this does not mean cutting into the filter material... maybe some of the glue, but they still work fine. i would also recommend the foam style pods and not the pleated see through "filters"

imo, drilling main jets is fine to find the best size if you dont want to buy a kit.... maybe even long term. never pilot jets or needle jets.

Great info on shocks: www.cyclecycle.info/bicycle-compatibilit...ort=asc&order=Length
Last edit: 10 Aug 2020 09:37 by Saablord.

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10 Aug 2020 15:33 #832592 by Mikaw
Replied by Mikaw on topic 78 kz750b build
How do you equate a drill size to the jet size. I just check a .043 drill bit or about 1.08mm is about a110 jet. Sounds like a solution (jet) looking for a problem. Jets are cheap and you get correct sizes.

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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11 Aug 2020 13:38 #832662 by timmdur
Replied by timmdur on topic 78 kz750b build
Simple... Use those teeny-tiny jewelers drill bits with a hand chuck. And be super careful. :laugh: They come in more sizes than there are jets! I've drilled some for a vw based dune buggy I have, and it turned out alright. I get that these are different waters, but we'll see how it goes! And why the heck not try it if I have a handful of spare (incorrect size) jets?

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03 Sep 2020 06:41 #834285 by timmdur
Replied by timmdur on topic 78 kz750b build
Well, I felt like I was making good headway, and then college hit... I haven't done much to the bike, but I have done a lot of studying! I synced the carbs with the old string and popsicle stick trick (I'll do it better later), and I started planning what I want to do for suspension. I bought a set of forks from a '99 R6, but it turned out that one of the outer fork tubes was bent slightly. I got a great deal for just one fork anyway, and someone happened to be selling a left tube on ebay for a decent deal. I think that the steering stem is long enough to use an All Balls kit, but I'm gonna make sure before I buy bearings. I also picked up a rear shock from an '08 Buell 1125r, and I plan on rebuilding the rear subframe and suspension. Unfortunately, a nice tube bender and dies is out of my budget, so I plan on building a template out of PVC, doing a couple of dimensional sketches, and giving it to a fab shop to make. Anyone have an idea of how much that would cost?

Oh! I almost forgot... I gave up on the starter motor, and I didn't want to spend $200 for one on ebay, so I drove up to the Poconos and picked up a spare engine for $100... If anyone needs parts, let me know! Supposedly is has fresh pistons, so I might nab them for mine. We'll see!

A couple days ago I got the bike started and idling a bit. It's running really lean due to the pods, so I think I'm gonna try 50 pilots and 150 mains. We'll see where that gets me to start. Tonight or tomorrow I plan on fiddling with the carbs some more and changing the oil and filter.

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03 Sep 2020 09:01 #834294 by Skidmark
Replied by Skidmark on topic 78 kz750b build
VW based dune buggy, you say? Here is my "other" recreational vehicle....

Retired gearhead
'81 KZ-750 E2
'87 Suzuki Savage 650 Street Tracker (lost in the shop fire)
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03 Sep 2020 13:34 #834315 by Skidmark
Replied by Skidmark on topic 78 kz750b build
Sorry for the hijack... now back to your regularly scheduled program.

Retired gearhead
'81 KZ-750 E2
'87 Suzuki Savage 650 Street Tracker (lost in the shop fire)

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03 Sep 2020 13:44 #834317 by TexasKZ
Replied by TexasKZ on topic 78 kz750b build
You should talk to Les Holt at PDM about your swingarm. There is a link at the bottom of the page.

1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough

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