Recently picked up a project 1987 GSXR-250. The previous owner had ridden it for about a year before it started running poorly and he got fed up trying to fix it. After cleaning the carbs it ran though only on choke, through it was going it was smoking quite a bit but put it down to not having run for nearly a decade. All four header pipes got hot also. Then I pulled the valve cover and double checked the valve clearances which the previous owner adjusted. All but one was on the upper end of spec and one was slightly over so no issues there. When turning the engine over though it felt like it had very little compression, so I pulled the plugs which did reducing the resistance but only very slightly. Unfortunately, I don’t have a compression gauge to confirm this, but it feels like it has very little. After pulling the exhaust I found that cylinders 1-3 were quite sooty but cylinder 4 was both sooty and oily. The consensus on here seems to be that it is an issue with the piston rings so will have to drop some oil into the cylinders to confirm, though I wouldn’t be surprised if it was the head gasket also. In terms of getting replacement rings a quick google search brings up a selection on eBay and AliExpress. Am a bit sceptical of the quality of these, so was wondering if anyone has used them before. Head gaskets also seem to be quite hard to get hold of though someone recommended using Copper Coat and was curious if anyone has had success with that as well. Look forward to hearing your suggestions. Darcy.
Welcome, That's in sensational condition, it looks great. Check this thread for info on the pistons and rings from aliexpress https://www.2fiftycc.com/index.php?...2-racing-in-california.8371/page-2#post-94334 Rings weren't enduring so great, but he was pleased with the pistons. That's in a racing situation mind you... I've got a set of aliexpress piston rings for my FZR250, measured them with a micrometer and they are accurate as far as thickness [height] and depth and finish quality is very good, there is even a laser etched alpha character to denote which way is up on the top two rings. @maelstrom also put a micrometer on a set of OEM FZR400 and aliexpress rings to compare, they measured up very well for him. Not so scare you but, reason I'm mentioning it is because my FZR250 sat for years and some of the cylinder liners are kaput due to small amounts of surface rust that are just enough to show as small depression looking through the cylinder into the light. So depending on what you discover with the bores, you may need to go oversize. Potentially depending on availability of OEM parts you could go OEM rings and aliexpress pistons. I know for certain that @Linkin has used successfully aliexpress pistons and I suspect that @Murdo may have also. AHL seems to be a trusted aliexpress seller for bike parts. I took a punt and bought a set of MC22 valves from an aliexpress seller [these valves used to be listed on the AHL aliexpress shop, they're not anymore] and they're all a bit under on the stem diameter. So I suspect that AHL may have some quality control in place. Not being a dick, but I do have info from someone that's into FZR400's and he got a PM [personal message] from a UK based company that deals with every sort of conceivable FZR400 racing mod and part, and they said they've used aliexpress FZR400 pistons. I don't want to name names as that information was given in confidence, but it's reliable information. EDIT - got bored and checked Impex, Webike and Mick Hone for rings - part number: 12140-05C00 Seems you're in luck, please verify that part number which I got from here https://en.impex-jp.com/catalogs/moto/suzuki/9900b-68022-020.html BTW have you checked impex for parts? https://en.impex-jp.com/ Rings ~$47USD [shipping extra] - https://en.impex-jp.com/parts/new/search.html?partNo=12140-05C00 also there is webike https://japan.webike.net/ Rings ~$52USD [shipping extra] - https://japan.webike.net/products/25711049.html As they seem to be available from Japan - same part used on models extending into the 2000's Locally - Mick Hone - ~76AUD [comparable to the USD Japanese prices] http://www.mickhone.com.au/part/suzuki/1214005C00#content I've been cross referencing between impex and webike of late, prices are comparable between them. I've got some copper coat for a NLA base gasket which is to be reused, I did do a fair bit of reading before purchasing, so hopefully my faith isn't misplaced, plenty of people report reusing head gaskets successfully with it also. hope this helps
Nice looking bike and quite rare. You can get head gaskets custom made. Gaskets to Go does them here in Thailand and Cometic in the USA.
G’day Ruckusman, thanks for the quick reply. Pulled everything apart and took as many measurements as I could, and the results of the autopsy are in: Piston Rings 1 0.229 0.356 0.279 0.356Spec 0.10-0.25 2 0.254 0.305 0.356 0.305Spec 0.25-0.45 Piston Skirts 48.93 48.95 48.93 48.91Spec 48.955-48.970 As for the valves, cucked some petrol in the combustion chambers and let it sit for a little while and all looked good. Also, the head gasket looked absolutely fine. No evidence of blowby or rust, only some of the paint had wrinkled around the water jacket. The bores mostly looked good. The crosshatching looked like new and there were no scrapes or much of a glaze. However, on cylinders 3 and especially 4 there was some discolouration on the sides of the cylinder. Running my fingernail over the marks I couldn’t feel anything, and they were only visible when viewed from certain angles. Thanks for all the links, this is the first proper bike I’ve worked on so nice to know where to get parts. Unfortunately, they don’t look like they have oversize rings (12140-05C00-050 and 12140-05C00-100 I assume) so might be stuck with the AliExpress rings (Oh well I’ll call it an experiment). Other than that, I can get a 0.5mm overbore from the local machine shop pretty easily since I used to work there, if you reckon that’s what it needs.
Whatever you do make sure you stick to the tolerances shown in the manual... these older Japanese high reving engines have nice tight tolerances and there are plenty of places who are used to cars or big lumps of American Iron that will tell you they cant possible work with those tight tolerances..
Those bores look like mine, I took one of the worse ones I removed from the cylinder block and gave it a going over with soap and steel wool this morning - rust discolouration is still there and I think it would wear down and discharge the rust and become tiny pit with time if it were put into service - so I'm going to swap the two good removed ones with the two poorly looking ones that are still in another cylinder block to get 4 reasonable ones. I would overbore with aliexpress pistons, but the standard bore cylinders are going to be temporary. Shame they list the oversize rings, but it looks like they maybe only ever produced them in small numbers a long long time ago.
Alright, will put in the order in for the oversized AliExpress pistons and rings and put it for the overbore. Thanks again for all the great advice, coming across from old diesel Land Rovers I probably wouldn't have looked twice at those marks so sounds like you've saved me quite a bit of hassle.
One of the other bores which is still installed in the cylinder block, after I'd honed it [with inox] the rust was gone and it's a tiny depression. I look at it this way, with tiny pistons whirling at such speed, every bit of the ring seal counts, so if it can escape through a section that the rings cannot possibly seal, that's going to have a detrimental effect. If you give those rust marks a spray with inox, leave it for a bit and then a scrub with one of the really fine steel wool pads I think the rust will lift off and you'll see the tiny depression. That's what mine did.
I just did a test, I took an stretched out paper clip and went gently across the marks on my cylinders - there's definitely both roughness and small depressions - it acts like a record player needle, I cannot feel that roughness or any depressions with my fingernail. I don't have a set of 4 good cylinders between what I have, so I'm off to aliexpress also for an oversize set as well - done!
