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Post by grizld1 on Apr 23, 2014 14:24:37 GMT -5
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!
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Post by goodgollyjosh on Apr 23, 2014 16:09:52 GMT -5
Yep, CR500, woops. Thanks for the info!
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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?
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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!
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jack
Junior Member
Posts: 99
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Post by jack on Aug 30, 2014 20:35:38 GMT -5
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. Can't believe PJ's short vid has been dropped .  |
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Post by crazypj22 on Nov 24, 2014 19:19:53 GMT -5
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 Found it, lets see if it works  vid91.photobucket.com/albums/k315/1crazypj/XS650/XS800.mp4 Bit disappointing is doesn't automatically load vid but, it's back. That's the long rod 800 motor, got to try and remember what exactly is inside it  |
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jack
Junior Member
Posts: 99
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Post by jack on Mar 15, 2015 14:57:59 GMT -5
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   |
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Post by crazypj22 on May 10, 2015 12:22:35 GMT -5
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
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jack
Junior Member
Posts: 99
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Post by jack on May 11, 2015 16:11:21 GMT -5
PJ sent you a PM,keep in touch.
Jack
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Post by hairball on Nov 26, 2021 6:49:41 GMT -5
A few points. As a rule, long rod XSs make more power. They are particularly advantageous in dirtack racing, as the short rods make for a more explosive mid-range, and coupled with the lack of flywheel, forces one to compromise midrange performance, typically by using Mikuni round slides and 1 3/4" head pipes, to get the bike to hook up out of the turns, or you just go up in wheel spin. Although this is necessary in the dirt, it makes for less than optimum performance on the pavement. Heavier pistons and rods are plus in a re phase, as it improves the balance factor for a quarter fire motor, which needs to be substantially less. That is, more like 50%, compared to about 65% for a stock 360. This why 750 re phases are smoother than 650 re phases. Hi Merc, newby here, working on a flatrack bigbore package and aquireing info on the direction of that package, sounds like you have experiance vs thery on this type of build, a couple of questions for you, does the use of a cr500 rod require a spacer under the cylinder, if repaseing is done what rpm range would it peak at, also whats the max bore diameter if useing stock liners ? Has anybody tried boreing out the liner and using nickisil treatment or is the casting not lend to that? thanks in advance |
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Post by olldernwiser on Nov 22, 2022 20:49:23 GMT -5
may i inquire as to what site you found this info on? What are the valve specs on an XS2 camshaft |
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