FZRSupport: the FZROnline Archive

Hi all,

When i bought my 1989 FZR400 1wg a few years back I did a valve job, complete gasket change, and other misc fixes and restorations but never rebuilt it (pistons and rings). Once i put the engine back together and everything and did a comp test i was only getting around 90psi in each cylinder which i know isn't great but at the time for me it was good enough to ride for a while since it was a daily rider back and fourth to my high school down the road and then some twisties rides. now that a few years have passed and ive been working on it each year to fix something I am debating on rebuilding it this year. I need to do my fork seals so ill be ripping the front end off no matter what so i was thinking about just going full out instead.

I am not sure if you order a OEM piston off say Partzilla or a local Yamaha dealer if they come with rings, i don't think so since on Part sites they are separate from the pistons.
One thing i do not know at the moment is what size my pistons currently are so that will also be a deciding factor if i start to rip it apart.

Also if i do rebuild it, what things should I be doing at the same time as the rebuild? (like head skimming and stuff? I plan on checking all the surfaces if i do take it apart with a machinist straight edge) And should I dive into my false neutral issue possibly? Some people on Facebook forums said that i should try to adjust the clutch actuator(on the sprocket cover) as i have already tried moving the shifter down I can feel the dog gears click in and out between shifts so I know something isn't right.

Lastly, what are the best brake pads to use? I have repainted my wheels about 3 times now (once the first year i had it then 2 times last year since first paint job on it went wrong) but after almost every ride with not even hard braking my wheels are COATED in brake dust, i literally have to blow out my calipers every few rides because they get coated too. I really hate having dirty wheels as it ruins the look of the bike with the fresh white wheels and wondering best type of brake pad to use to get minimal dust and still good braking. (i was also debating throwing a set of FZR600 twin pot calipers on but maybe later down the road)

thanks, AS

Before you pull it apart I would check to see if you can get new pistons at all. On a previous FZR400 of mine I had really low compression on one cylinder so I pulled the head and cylinder block. The one bore was badly gouged so it needed a rebore. The pistons were already two sizes over but luckily in usable condition as I could not find replacements in any size anywhere even after-market. I ended up buying a stock bore cylinder block off eBay and had it rebored to fit my pistons.
If you find replacement pistons let us know!

Well on Partzilla I have seen STD size pistons become available about once in the 3 years which i should have scooped them up at the time. This site says there are some available apparently: https://www.motosport.com/oem-parts/par ... aft-piston

When i had the jugs off the bike the bores looked just fine so i didnt think about rebuilding. Also, so say if my pistons clean up okay and have no damage to them, is it okay to just change the ring sets? because those are available for stock size easily. I would most likely change the bearing just because i am there and it doesnt hurt to.

Another thing i was thinking of doing was buying a set of jugs i found online since its cheap and i could have it all setup and quickly just swap the parts and have it rebuilt then.

I would caution about buying a cylinder block on line because you won't know if it's been bored out or not. Even a stock bore block will likely have wear so you would be looking at a re-bore one or two sizes over. Whoever does the boring will need the pistons to get the correct bore within tolerance. From memory the stock pistons were only available in two sizes over standard. Because I could not find new pistons I re-used my old pistons and rings and had no issues. Compression was great after everything seated in. It was my trackbike so it was thrashed to the redline in every gear and ran flawlessly until I sold it.

Why do you think it needs pistons ? Did you do a "wet" compression test with some oil down the bores.

Does it smoke a lot,use a lot of oil and are the plugs covered in oil ? Even if the ring are worn all you do is measure them and replace .... hone the bores but no need for pistons.

I don't know if it needs pistons to be honest, some people say to not reuse pistons some say it's okay, I have no clue. Yes initially I did a wet test and it was about 90psi I think in all cylinders. If the jugs are still clean could I not either reuse them and get the cylinder deglazed if necessary or just swap the rings and call it that?

But you don't know it's the rings.

Take a compression test dry and then add the oil, if the compression goes up then it's more likely the rings. If it doesn't then it's more likely the valves aren't fully sealing.
Over time the vales stretch and the flat area "tulips" up into the hole.

You only need new pistons if you rebore the barrels.

When i ripped it apart last time, the rings weren't perfect but they looked good enough to me. I will try the compression test variations when I pull the bike out soon to do the fork seals and such maintenance. When i had it apart i did lap all the valve seats so they should have been pretty good. I did have a leak down test done at one point and I never heard much coming through anywhere(listening through the exhaust pipe). Valve clearances were all in spec as well because that was the main reason i had to pull it apart in the first place.

i'd rather not rebore the barrels just because thats a little more than i as hoping to invest this year. Also to answer you before, it smokes a lot on start up(thats normal with condensation), but otherwise no not a lot of smoke. It used to use a lot more oil but i learned to find i had a camshaft cover leak so after i fixed that last spring this season has used a good amount less oil but still more than i would like to because I am running 20w-50 and if i was running the stock 10ww-20(or 40 i can't remember) i would be burning a lot more. not sure how the plugs have been looking, i haven't checked them for about a year but I will probably replace them this season.

10/40 w semi synthetic. If the rings were gone you'd get blue smoke from it, it would be after you throttle off while moving.
Fit the right oil.

I do get some blue smoke now already when taking off but I not sure if that's because I have a slip-on exhaust that probably needs to be repacked but I have yet to do so.

So I recently bought a transmission off eBay that was $25(on sale) used for spare parts just in case. But I came across an airbox today which I've been told to get many times on here for better tuning since I only have pod filters. It says it's for an FZR400r so I'm not sure if it will fit my 1989 FZR400 1WG. The ad says it's frame number is 1WG-0376. My bike runs good as it is already but I'd like this just in case I want to return everything to stock since you can't find these anywhere anymore.

Here's the ad:
https://rover.ebay.com/rover/0/0/0?mpre ... 2848047198

According to the 1WG number in the listing that would make the donor bike a FZR400SP:
http://www.madsi.co.uk/models.aspx

Do the carb joints line up the same? I would assume so as they are still the same 1wg motor if I am correct.

I have a 1WG and a 3EN1 and the airbox appears to be the same on both even though the carbs are different. I hope some others will chime in on this. I see the one you are looking at is in Japan. I have seen airboxes come up from time to time on US eBay. I have found they run better with stock airbox. I had pods for a while and could not get it to run right.

A 3en1 is a 1wg.

1wg is the model type from Genesis up to 3en2. If a part is common to more than one bike it will probably be labelled from the earliest model so this would be 1wg ... then 2tk then 3en etc. Its like 3en1 downpipes are labelled 2tk.