Crawdaddy 96 Posted December 7, 2011 Two Stroke owners - Do you folks always close your petcock when adding a "field mix" of oil to your tank after filling at a gas station? Is there a concern that the oil could run straight to the carb if the petcock is left open? I added 2 gallons of gas to my 300 XCW, dropped in ~4.5oz. of Moterex, shook the bike from side to side, rode about 3 miles, and the bike just quit when I got up to about 50mph......as many of you know, the piston showed detonation damage on the exhaust side but the bike ran fine prior to the stop at the gas station.....I'm wondering if I immediately created a super lean condition by not closing the petcock when pouring in the oil? That said, there was still a gallon of premix in the tank, I shook the bike from side to side after dumping in the oil, and I didn’t let the bike sit for more than a couple of minutes before riding off.... Share this post Link to post Share on other sites
dirt dame 559 Posted December 7, 2011 Hmmm, never thought about closing the petcock. Motorex disperses quite nicely compared to old style petroleum based oils, some of which need a dispersing agent such as a Stoddard solvent to get them to mix well. I just fill up the tank, pour in the closest ratio of oil, cap it up and grab the front brake so I can rock the bike back and forth for about 30 seconds. I let the vibration and movement of the bike do the rest. I never pin my two stroke on the pavement though. I only run it at the upper range of loafing speed, which in my case means that the bike will never see more than about 45-50 miles per hour. I like to vary the throttle a bit too. Share this post Link to post Share on other sites
Crawdaddy 96 Posted December 7, 2011 Thanks for the prompt reply Mimi. I don't think I had the bike pinned when it cut out but I'm sure I was at ~3/4 throttle in 4th (probably?) since we were heading up S22 out of Borrego Springs.......we also had a good ~10(?)mile pavement run into town before lunch/gas......but I kept my top speed around 55-60 in 5th.....that's well below "pinning it" on that bike..... Share this post Link to post Share on other sites
Spaugh 1 Posted December 7, 2011 did you ever get a compression test done? Share this post Link to post Share on other sites
Crawdaddy 96 Posted December 7, 2011 did you ever get a compression test done? Compression was 170 when I picked it up. Share this post Link to post Share on other sites
Spaugh 1 Posted December 7, 2011 taken by you or the PO? i suggest having RJ do it after it back together to make sure it still in that range. btw, i never shutoff my fuel when i add oil on the go. it seems like your bike should have been blowing coolant if it got hot enough to melt a piston. Is it possible it was low on coolant or was running the no boil stuff? Share this post Link to post Share on other sites
paulmbowers 236 Posted December 7, 2011 I'm no expert, but wouldn't a fuel mix overrich with oil just foul the plug? Share this post Link to post Share on other sites
Crawdaddy 96 Posted December 7, 2011 taken by you or the PO? i suggest having RJ do it after it back together to make sure it still in that range. btw, i never shutoff my fuel when i add oil on the go. it seems like your bike should have been blowing coolant if it got hot enough to melt a piston. Is it possible it was low on coolant or was running the no boil stuff? By previous owner.....he sent me pics of the gauge attached to the bike showing the reading......trustworthy guy. The bike had Zipty waterless coolant so no boiling over...coolant level was ok but the coolant looked pretty nasty when they emptied it out at AAKTM.....not sure how long it had been in there..... Cylinder is at Millenium now. The head was modified for higer elevations by Jeff Slaven as part of a Slavens Mule Mod......AAKTM will check compression/squish and do whatever needs to be done to LOWER compression when they put it back together.... Rec'd this email from Jeff Slaven this morning: "Chris: Sounds like you may have had the perfect storm with a combination of issues. I suspect that you may have had a combination of slightly lean jetting from cool winter temps, a loose rod bearing causing higher compression, and possibly the head was machined for higher elevation. I don’t have records about the head machining. When you complete the rebuild you will need to check the compression with a high quality screw-in guage that has a ¾ reach threaded area. Hold the throttle wide open and hold down the kill button. Kick (about 20 kicks) it until the gauge stops moving. Email me the results. Also, put the needle in the #3 position. Also, please watch my carburetion video." From: Crawdaddy@Crawdadoffroadevents.com [mailto:Crawdaddy@Crawdadoffroadevents.com] Sent: Wednesday, December 07, 2011 8:48 AM To: jeff@slavensracing.com Subject: New Message from Slavens Racing New message from Chris Crawford Mail: Crawdaddy@Crawdadoffroadevents.com Website: http://www.Crawdadoffroadevents.com Message: Hi guys. I bought a 300 XCW from Mike Jones in Tucson, AZ. The bike rec\'d a Slavens Mule Mod at 210 hours and had 375 hours on it when I bought it (~50hrs on recent top end). The bike also had a JD kit installed. Mike had the bike jetted for 5-8K feet so we changed the jetting for my Sea Level to 3K\' winter riding in the San Deigo area. We made the changes per the JD kit instructions (162 main, Blue needle, #2 clip, stock pilot). Long story short, the piston grenaded after about ~150 miles of riding in my local deserts. It was under load at about ~50mph. Detonation burns on the exhuast port side woudl seem to indictate I was running too lean despite richening the carb settings and running at a 50:1 mix versus the 60:1 Mike said he always used. I honestly don\'t know if I had bad gas (doubful), too lean a carb setting (seems likely) or the bottom end was just sloppy after ~380+ hours.......or a combination of all of the above..... So now I'm rebuilding the top AND bottom and my question is whether the Slavens Mule Mod increases the compression such that I need to go even fatter on jetting? I'm planning on going back to KTM needles/jets. Do you folks have recommended carb settings for the stock KTM needles/jets at various altitudes post Slaven Mule mod? Thanks and Regards, Chris Share this post Link to post Share on other sites
Spaugh 1 Posted December 7, 2011 i'd ditch the no boil stuff. everyone i know that runs that stuff has mysterious bike issues. a boiling radiator is a good indication to stop riding that nasty single track for a minute until the bike cools down or in your case pull off the highway and change your jetting. just my .02 ps, if the 170psi the PO read was at 5000ft, that would be equivalent to ~205psi at sea level which will cause damage running pump gas. Share this post Link to post Share on other sites
Guest Crusty Posted December 8, 2011 Next time you ride the pavement pinned on a 2T hit the kill switch once a while, to richen it up. Something I was taught to do by a fellow Grand Prix racer, back in the day. I always wondered why there were so many skid marks at the end of the pavement sections. I was also taught to keep two fingers on the clutch, this saved me once. Share this post Link to post Share on other sites
daijones 0 Posted December 8, 2011 I would always shut off petcock then put oil in the side of tank opposite the petcock and fill tank, shake to mix before opening petcock. But as Mimi said with modern oils like mototrex shouldn't be an issue, old oils could even block petcock filters or if you got a very high oil mix sucked through it would give a short term gas lean issue but doubt that would have been cause with motorex especially after a few miles but possible. Share this post Link to post Share on other sites
Zenosan 2 Posted December 8, 2011 Never heard of the closing the petcock either. However, it was a given with long range desert two strokes that not varying the throttle would cause an overheating condition. I did it myself and learned the hard way by siezing a piston a long way from camp. If you were cruising on pavement at a constant speed for a long time it is likely this could have been the culprit. Share this post Link to post Share on other sites
Crawdaddy 96 Posted December 8, 2011 ps, if the 170psi the PO read was at 5000ft, that would be equivalent to ~205psi at sea level which will cause damage running pump gas. True....never thought about that. RJ said it looks like the Slaven mod shaved off about ~.025 from the head which makes the squish pretty tight/restrictive/sensitive to adjustments in jetting, etc. May wind up using a different/spare head at AAKTM rather than trying to build the squish back up with extra gaskets or (?) on the head that came with the bike. Good points about sustained speeds on a two stroke......I'll need to remember to vary the throttle a bit.... Share this post Link to post Share on other sites
