Josh, all I know is that the needle bearings Yamaha used didn't hold up well to the pounding they got from the 4-stroke motor; I suspect Mama's engineers may have made some assumptions based on 2-stroke power pulses. I don't think lubrication was the issue; if that had been the case things would have been even uglier with the solid wristpins, as no changes were made to the lubrication system. You're dealing with rods and bearings designed for a 4-stroke application, so you're probably good, and it sounds like the small end of what you're using is more robust anyway.
Did you mean CR500 rods? The CB500 had a 4-cylinder mill, and I pretty sure those rods aren't what you're using!
Last Edit: Apr 23, 2014 14:25:53 GMT -5 by grizld1
Post by goodgollyjosh on Apr 25, 2014 11:25:58 GMT -5
Thanks Kop, I have seen some of your posts both here and elsewhere, sharp cookie. Mighty nice pistons BTW. I have to admit I stole some of your deck height dimensions because I was having trouble calculating this once I discovered the planes were not parallel. This is not something I have run into before. I have had good luck with .040" quench in auto engines. Got greedy and went to .035", ran well in a circle track app. Went to .030" ran great the whole season, tore down for freshen and saw fretting where the piston and chamber were kissing at high revs. So, I backed up to .040", I think I will stay there for a while. I give it another .020" (total of .060") when dealing with aluminum rods. Seems un-effective above .060" with a steel rod. The angled quench of the XS is a different animal. Never been a huge fan, at least not with Hemi style chambers in auto engines. I can make peak power at 34-36 degrees ignition timing with a flat top and fast burn chamber. But the 426 acts like an XS in that it wants more in the range of 42 timing (well, this is here say because I don't know on the XS for certain but the factory manual has it listed as such). Gotta hate a lazy flame front. Any thoughts?
Post by goodgollyjosh on Apr 28, 2014 11:03:45 GMT -5
You are doing a great job! Fine with me though, I dig this kind of stuff. .037" deck clearance is a very specific number, you have definitely been around these motors a while in order to have dialed something in that close. I will watch it then because I am at .040" on paper, hope to have some actual numbers soon. Thanks for the tip on the back cut, I didn't do it on the intake valve or either valve for that matter. You will have to fill me in on the front cut, that is not a term I have used. The three angle valve job is not blended and the seat venturi in the intake is currently at 85% of the intake valve diameter. Not looking to break any records with this motor, just something to play with on the street and maybe the occasional blast at Texas Mile or the drags. "A rate of angular change extrapolated as a non linear output for your experimentation". You remind of a few guys I work with. :-) Thanks for the info!
MTC GPZ KZ 1100 pistons would be the ideal alternative non custom piston for the CR500 rod as it has a compression height of .1020 ,18mm pin, 78mm to minimize block boring cost, weight in at 383 grams with a 13-5 compression dome for modifing. These particular pistons have more of the ideal dome shape for what little squish pads the XS heads have, better alternative than the KZ900 pistons I bought. Been in contact with MTC about pricing and certain mods and for two it'll run about 284.00,not a bad deal.
Hi Jack, long time since I logged in here. Pretty much given up on XS motors since I was laid off in 2011 I don't think it was deliberately dropped, just lost when new site went up. I have trouble finding it, if I can I'll just re-post the running long rod 800
PJ......sorry to hear about your job situation and hopefully your vacation didn't last long,been down that road myself several years back. Hers'a a photo of the GPZ 1100 piston 12.5 and milling it down to 11.0 would be a ideal for starters and re-cutting valve pockets. Thanks for re-posting your long rod vid,hopefully by my retirement,mine will be up and running
Hi Jack, things haven't improved, in fact things have gotten much worse. I didn't set an appointment with hand surgeon so insurance company has now said it's passed statue of limitations. I feel I was conned into getting an insurance Agent Licence by Bankers Life and Casualty company, 1099, zero sales experience, promise of training and leads. The training wasn't too bad but the leads were just lists of people turning 65. I wasn't dishonest enough to sell insurance and felt like a telemarketer trying to set appointments. Only lasted 5 weeks before I was told to write a letter of resignation I didn't but was escorted off the premises after they checked I had no information or papers connected to Bankers Life Anyway, the pistons look real good, going to have to start saving for a pair (or set, I forget if I have one or two cylinders bored to 78mm) I did buy a pair of XT350 pistons many years ago but didn't get any further with 84mm bore All for now PJ
There are three types of people in the world, those who can count and those who can't I dabble in rocket science, when I'm not picking my nose
r80rt: :)This is a splendid write up, THANK YOU!!!!
Dec 26, 2015 16:54:05 GMT -5
mashermoto: What the what is this shoutbox for? Or should I shout, WHAT THE WHAT IS THIS SHOUTBOX FOR!
May 12, 2016 22:22:21 GMT -5
motormike: Good Day ...just a FYI.. Wild Cat is this Labor Day weekend. Still go'n on. A few 650's still make the scene. Various rides at different skill levels each day.. awards dinner sunday eve. BS in the park'n lot after dinner.
Aug 23, 2016 7:57:01 GMT -5
lsettle: First post in over 6 years!
Aug 28, 2016 19:45:17 GMT -5
kardon: Wow quiet here, where did they all go.
Oct 7, 2016 2:18:13 GMT -5
gggGary: XS650.com LOL
Feb 16, 2017 20:49:02 GMT -5
buell88: Anybody have any idea who built the xs650 tracker used in the Draggin Jeans Ad on Pipeburn?
May 16, 2017 16:24:09 GMT -5
joshua: The regulator/rectifier unit I got from Mikes PMA has closer hole spacing than original. Are we supposed to mill the holes to fit?
Jun 7, 2017 19:25:58 GMT -5
joshua: My bad. I found the bracket they supplied to mount the rectifier/regulator... Uh oh. How is this meant to work? Which way is it meant to mount? Looks like I have to use some spacers or something. Good instructions would be nice.
Jun 7, 2017 22:09:52 GMT -5
craig8johnson: Not sure if this is the right spot or not but oh well...
Jul 11, 2017 18:04:15 GMT -5
craig8johnson: I'm checking the charging system. I'm afraid I might have fried the last battery. With the solid state regulator (after market) what should it be charging at. The book says, I think, 15 volts. I'm hitting 17 when revved. Is that too high?
Jul 11, 2017 18:06:19 GMT -5
gggGary: Yes 17 volts is too high, about 14 volts is max, sounds like you don't have the right regulator or it's wired wrong.
Jul 13, 2017 6:54:33 GMT -5
dean: Just saying Hello, new member who is going to fix up a 79 XS650 that has seen its better days. I will definitely have lots of questions coming up.
Jun 23, 2018 16:45:32 GMT -5
tt650: Trying to breathe life into a 1980 that's been stored (indoors) for 25 yrs. Air filters are dry rotted. Have cleaned carbs but she only runs briefly on choke then stops. Need jet setting info and other ideas that might help her idle and rev.
Jul 3, 2018 19:15:19 GMT -5
trix13: Hey everyone! New to the forum and am fighting those gremlins!! New charging system, ignition switch, coil and fuse box. Resistance is higher than normal on the ignition pick up so I'm trying to find one. No such luck yet.
Aug 16, 2018 8:50:48 GMT -5
trix13: Also, even though all of my connections are clean, I cannot seem to find out why , when at higher rpms, I hit the signals and the rpms pulse with the signals...hahah. same with the brake light. I appreciate all input!!
Aug 16, 2018 8:55:08 GMT -5
bob99: how do I post a question. I am new to the forum
Jun 6, 2019 10:52:10 GMT -5
adlpc: Hello all! Been enjoying your edifying posts and discussions - and as a fan of the XS650 since my early teenage years happy that I now own a 1980 Special which I plan to turn into a vintage half faired racer. Thank you all for being here!
Oct 1, 2019 0:58:56 GMT -5
jimothyj: Hello everyone, I just joined & wish would have known about this site in 2014 when I brought my 1974 TX650A back from the grave. I have spent a good deal of $$ and alot of time on it. Just painted it and working on electrical, I will post pics soon,
Apr 10, 2021 2:14:13 GMT -5
louisvan: trix13 - I had a problem with my 1975 SX650. When I got to highway speeds, the engine lost power. The problem was in the connectors. At a certain vibration and the wind pushing on the wiring loom, the connector lost continuity. A bad crimp to the wire.
May 20, 2021 1:19:09 GMT -5