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As for if the petcock fails you won't just get a sniff of gas in the oil, it will fill the case to the top.
Interesting - didn't know that, but have never owned that bike before, so maybe I should have been more circumspect in my reply to Zed7.

Apologies Z.

Live and learn.
 

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Discussion Starter · #22 ·
Interesting - didn't know that, but have never owned that bike before, so maybe I should have been more circumspect in my reply to Zed7.

Apologies Z.

Live and learn.
No worries. Happy New Year. 馃嵒
Well I bought the 7S and have stripped it down for a cleaning and maintenance. And I was very surprised, when removing the tank, that the petcock wasn't leaking. The ZRX is famous for it. If you notice how high the carb vents are, a leaking petcock combined with a faulty float valve will fill an engine with gas quicker than you realize.

Before I start the ZRX, I always look at the oil level site glass with the bike on the side stand. Normally no oil should be seen. If you do see oil with the bike leaned over that means you have gas in the crank case.
And I can also stand the bike up to check the oil level before starting. If the cold oil rises to fast, that means the oil has been thinned by gas. 20 years of ZRX ownership will do that to you.
 

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I'm mega-late to the thread but I'm winding down from 7 hours driving and 8 hours working today.

I bought my '01 in 2013 with 12k miles on it. It now has 21k miles and I haven't done a valve check. I THINK I can hear a ticking on top of #4 cylinder but the bike runs so good, I've been reluctant to pull it apart just to check after all this time. Other than plugs, filters, oil, and Seafoam, the only thing I've done to the engine is make sure the carbs were balanced. I bought a set of gauges to do that early and then loaned them out to Smash, whose girlfriend had a 7, and I never saw them again. Bought another set of gauges to check and they were still balanced.

I posted a very detailed thread on brake rebuild back in 2014 I think; several folks on here gave me a lot of advice and help and I spent almost $500 rebuilding the brakes and replacing lines WITHOUT changing the pads! It was a good project, though. I had a $400 custom seat made by Loren Mock at Baldwin Motorbike Saddles, who I think is either deceased or completely out of the business (he disappeared). I did the aluminum tail tidy which I really like. Biggest expenditure was replacing the suspension: RaceTech front fork full rebuild with Gold Emulator and Nitron rear shock.... $1700!!! The front is completely new except for the OE lowers (they talked me into new uppers). But I can definitely tell the difference for the better and there is no more dive and no upset over crappy asphalt. EDIT: at first, I did the PVC mod to the fronts and noticed a difference. I LOVE the RaceTech forks though, especially since I paid a pretty penny for them; take that as you will, but they are noticeably better than OE or PVC mod or Chinese adjustable fork cap mod.

I did a chain and both sprocket replace with a 17T front, which was great for lowering RPM slightly. Smoked Zero Gravity touring screen, battery tender pigtail, GoCruise attachment, phone charger mounted to handlebar. The 7 is a great bike for just tooling around or touring medium distance. Mine's not perfect but I know her pretty well and she gets 52 MPG with very little attention.
 

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DF. good to "see" you again.
 

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Discussion Starter · #25 ·
Daddy Flip, about the valves. They are not a "if it ain't broke don't fix it" type situation. You MUST check them, probably now.
As I said, I'm the 3d owner. 2nd owner didn't check them. 1st owner, I don't know if he ever had them adjusted. But judging the way all the bolts came out I'd say no. There were no overtorqued fasteners, a sign that somebody has been in there before. Nothing knackered.

Here's what I found...
I first checked compression.
1- 125 psi
2- 45-50 psi
3- 110-130 psi
4- 130 psi
Then I squirted some oil in the holes...
1- 160 psi
2- 150 psi
3- 160 psi
4- 170 psi

So worn rings. Maybe not. I know that's a sure sign but cannot the oil splash up to the valves?
Checking the clearances this is what I got. (And I bought my very first METRIC feeler gauge set. 馃憤 Oh happy days. What was I thinking all those years doing this with an inch set. Madness).
Three of the intake valves were at the low end of the spec .08/.09.
#1 intake was below spec at .05

#1 exhaust was below spec at .05
The other three exhaust valves were tight, as in zero clearance. Judging by how easily the buckets rotated on #3 and #4, I'd say their valves were closing (my feeler gauge goes down to .03mm).
#2 cylinder- the lowest psi, its bucket was tight enough that I couldn't rotate it with my thumb. So I'm sure that when I get them in spec the psi will rise up and get in line with the others providing there's not a burnt valve.
I'm just waiting for my shim kit to come in. The kit was necessary because of the tight valves. I want all my valves at the .18 spec.

I should also point out that the engine had been sitting, not run, for about three weeks and it was cold, about 28 degrees F.
The PO had the bike running when I got there to buy it but he did he did mention it was hard to start. It ran well and strong on my brief ride.
There was no smoke from burning oil and all the plugs are burning perfectly.

If you, at least,check your valves, make sure you buy a head cover gasket and side cover gasket. They are going to rip when you pull the covers.
Also, there is a tutorial here about adjusting the valves.
I read it and did the cardboard boxes and sandwich bag system. It's an excellent system.
And make sure you buy a set of METRIC feelers. I bought a Tusk brand which starts at .03mm and increases by .01mm

And also, I understand your pain with your carb balancer that you leant to your friend.
I have a mercury set and it is the one tool I won't lend out owing to the fact that mercury is getting near impossible to buy. I will have my friends come to my house if they need to balance their carbs.
Oh, I won't lend out my newly calibrated torque wrenches either.

Cheers, make sure you post up the results of your valve check. You might get lucky.
 

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@Zed7, so yes the lower compression could be worn rings or bad valve clearances but it could also be stuck rings if it's not been driven much. You'll know better once the valves are done and you re-compression test it.
 

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Discussion Starter · #27 ·
@Zed7, so yes the lower compression could be worn rings or bad valve clearances but it could also be stuck rings if it's not been driven much. You'll know better once the valves are done and you re-compression test it.
Yes, it could be any of those. As soon as I get my shim kit and the engine running, I'll figure out how healthy it is. I'm positive it's ok. I've seen bikes ten times worse run without problems.
But it'll be interesting to find out.
This is what winter is good for ... to maintain your bike.

I was looking for a winter project when I stumbled upon a guy with a 1980's Yamaha 350 2 stroke. He is the original owner (who was willing to let it go cheap) and the bike had low miles but it sat for years.
Upon researching the bike I found out that I'd have to split the cases and take the crankshaft apart and replace the crank seals. This I didn't want to do. So I hit Craigslist just to see what was out there. That's how I found the zr7s.
We shall see. 馃憤
 

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Discussion Starter · #28 ·
Just a small update on my 7S.
I've pretty much stopped taking it apart and am waiting for the weather to cooperate as my shed is unheated. I have a small electric heater that'll raise the temperature only about 20F from ambient. If this was summertime I'd already be finished.

Everything is rebuilt and awaiting installation. The brakes, the carbs. The upgraded forks are installed, wheels cleaned and treated with a chemical wax. I put new tires and valve stems.
The front fender took a beautiful shine.
So next to go back on are the brakes, and next Thursday the temperature is supposed to hit 57F so that'll be my carburetor installation day. They'll be swearing and cursing going on that day but at least my fingers won't be numb. I've already repainted the engine case underneath the carbs.
 

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Discussion Starter · #29 ·
I also just added the 470 ohm resistor to the gas gauge so now I can put the front fairing back on.
 

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I also just added the 470 ohm resistor to the gas gauge so now I can put the front fairing back on.
All sounds good. You should have posted some progress pics
.
 

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Just a small update on my 7S.
I've pretty much stopped taking it apart and am waiting for the weather to cooperate as my shed is unheated. I have a small electric heater that'll raise the temperature only about 20F from ambient. If this was summertime I'd already be finished.

Everything is rebuilt and awaiting installation. The brakes, the carbs. The upgraded forks are installed, wheels cleaned and treated with a chemical wax. I put new tires and valve stems.
The front fender took a beautiful shine.
So next to go back on are the brakes, and next Thursday the temperature is supposed to hit 57F so that'll be my carburetor installation day. They'll be swearing and cursing going on that day but at least my fingers won't be numb. I've already repainted the engine case underneath the carbs.
If you live in an area with hot summer temperatures you may experience some fading in the front brakes. A good cure for that, if you haven't already put it in your plans, is braided lines. The stock brake hoses expand quite a bit when they get hot.
 
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Just a small update on my 7S.
I've pretty much stopped taking it apart and am waiting for the weather to cooperate as my shed is unheated. I have a small electric heater that'll raise the temperature only about 20F from ambient. If this was summertime I'd already be finished.

Everything is rebuilt and awaiting installation. The brakes, the carbs. The upgraded forks are installed, wheels cleaned and treated with a chemical wax. I put new tires and valve stems.
The front fender took a beautiful shine.
So next to go back on are the brakes, and next Thursday the temperature is supposed to hit 57F so that'll be my carburetor installation day. They'll be swearing and cursing going on that day but at least my fingers won't be numb. I've already repainted the engine case underneath the carbs.
Just make sure the boots go on the proper carbs (inner vs outer) and they went on easiest for me reaching thru the airbox. Some have said heating them up in hot water or with a hair dryer will soften them and help with the install, but I've never done that. Might be a help if you're doing it in the cold. You'll likely have scraped knuckles either way.
 

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I also just added the 470 ohm resistor to the gas gauge so now I can put the front fairing back on.
While not an important mod it's definitely a convenience thing - and very easy to do.
I often go by mileage as well, just because.
If all fails you have reserve (unless you're one of those who runs on reserve on purpose or by mistake.)
 

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Discussion Starter · #34 ·
Martin, I'm in Massachusetts where it's been very hot during the summer lately. I don't plan on pushing the 7 that hard but you never know. If the bike runs well I'll eventually get braided lines for the front. It's one of the first things I do once I buy a bike.

Obo, I did mark the intake boots as I took them out but a quick glance told me they were all the same. I'll look a bit closer. I cut in pieces one of those flexible nylon kitchen cutting boards, the type that's as thin as paper.
I install the boots then place one of the nylon pieces in front of the carb holders and the other in front of the boots then slide (jam) the carbs in. The nylon allows the carbs to slide while squashing down the intake boots but I like your idea of inserting the boots afterwards through the air box. I'll give that a dry run first.
Next I pull the nylon out of the engine side and insert the carbs into the holders. I repeat for the intake side. At least that's worked on other bikes. This one looks pretty tight and there's no give with the filter box.

Yeah, I should have taken pics. My bad.
 

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I had the carb holders already in place attached to the cylinder head. I then slid the carbs on to that. I then slid the boots on (if I recall correctly) feeding them in thru the air box with one hand and using the other hand behind the carbs to help line them up. Pushing thru the air box lets you apply a forward force and wiggle them around if you need more force on one side to prevent them going on sideways and binding up.

Check the 4 boots that go between the carbs and air box. The outers are either a bit longer or have more of an angle (I forget which) - also make sure the little notch on the top matches up to the peg on the air box.

122897


Here's some of the steps in my how to document (courtesy of others...)

Slide the bank of carbs back into place. Make sure you get them all the way back into the intake boots; you'll have to push them pretty hard. They should be stuck all the way in as far as they'll go. Then tighten the band clamps on all four carbs to hold them in place. Get the orientation of the screw clamps right.
122898


Replace the four rubber boots that connect the carbs to the air box. This is the most tedious, knuckle-scraping part of the job. Start with the two inside boots, and then do the two outside ones. You'll have to squish them down to squeeze them into the space they go, and then reshape them once they're there. It鈥檚 best to warm them up with a hairdryer to make them supple. Make sure you get them back in the same direction that they came out. Once you have them on the carbs, you can roll the retaining springs back up into the slots.
122899


There are little plastic pins sticking out from the air box at the top and bottom of each hole to help you get the boots back on correctly. The boots have little cutouts that line up with these pins.
122900


TIP - Stick your hand through the back of the air box and help pull the boots into place from behind. This will make it MUCH easier to get them back in place.
122901


The steps are then connect up the 2 breather tubes, choke cable, throttle cables, vacuum lines, fuel line, Ktric connector. (I think that's all of it...)
 
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Discussion Starter · #36 ·
Great write up. I have the gauge cluster on and front fairing mounted. I'm moving towards the back of the bike. Next up is the carbs. 馃憤 After reading this it doesn't look so bad.

I have some roll-rubber material. I'll just cut a small square and fasten it over the open sub frame holes with a zip tie.
 

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Discussion Starter · #37 ·
A couple of my motorcycle friends stopped by yesterday to check the progress of my bike. Though they helped me when I picked it up from the seller, this time they were genuinely interested in it, LOL.
I basically take it apart, clean, maintain or rebuild, and put it back together. It's looking better every day.
This bike is an anomaly.. an air cooled 750 from the eighties in a modern-ish motorcycle.
Of course the Suzuki Katana had one but they were making them for some time. Even Kawasaki used the 1000J motor in their police bike up until 2005. (I had one, a mint 2002 model that my brother now has).
If Kawasaki had used the 1000cc J engine instead of the 750, the zr7s would be a highly sought after bike. They would have sold way more of them.

I wonder if anybody ever made the swap?
 

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I doubt anyone ever did a swap but hey you never know. There was at least one person here who did the big bore kit for the zr7s (think it upped the 738cc to 810cc) - they rebadged the bike a ZR-8S. :)
 

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Discussion Starter · #39 ·
I doubt anyone ever did a swap but hey you never know. There was at least one person here who did the big bore kit for the zr7s (think it upped the 738cc to 810cc) - they rebadged the bike a ZR-8S. :)
I saw that thread. It would be worth it if you were rebuilding the engine. There are tons of mods for the 1000. Guys drag race them to this day.
The 1000 engine was something like 85rwhp. Not ground shaking but for its day was really something. I actually 'detuned' my police bike much to my friends' dismay. I was planning on touring with it but in police form it only got 30-33 mpg and only has a four US gallon tank!
I rejetted the carbs and changed the sprocket sizes for slightly less RPM on the highway. My end result was 45-50 mpg. I kept the main jet large for wide open throttle acceleration in case the urge hit.
I made the jet needle swap with a guy on the KZ Rider site. He was anxious to get a nice set of KZP needles as they are rare. Along with a set of CSR needles he also gave me great advice. When I reinstalled the carbs the bike ran perfectly without any issues. And it does to this day. I didn't want to give up my KZP needles, preferring to buy the CSR needles instead but the member who helped me out wanted to use them in his 140hp 1000 engine.
We had a great conversation over the phone. I never found out what his final results were. He was old. I hope he made out ok.

I don't mind the 750 in the 7S as long as it is reliable. I have a couple of more powerful bikes and it's very rare when you need full power.
 

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I did find the 17 tooth front sprocket upgrade helped with the ride. It made the bike less buzzy at highways speeds.
Perhaps it was all in my head (and all the others who've done it,) but the cost was minimal. Think the front sprocket was around $20 and I already had a grinder to shave the required bits off the sprocket cover. If/when you replace the front sprocket the cost for an OEM 16 tooth is usually about the same as the 17. Plus you will hunt less for the missing 6th gear :)

I've had both the Sunstar and the JT brands - there's no discernible difference.

Here's snipits from my Excel spreadsheet that calculates data based on sprocket sizes, rear tire size and engine speed.

17 front, OEM 38 rear (1st and 5th gear)
122903

122904


16 & 38 OEM (1st and 5th gear)
122905

122906


If you wanted more gears or adjusted front or rear sprocket sizes let me know and I can plug the numbers into the spreadsheet.
 
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