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Chuck. last won the day on November 23 2010

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About Chuck.

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    DIY guy w/ a plated Honda CRF250X and a Honda-Montesa 315R.

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  1. And you need carbide burrs and bees wax as a cutting lube. Most home air compressors don't have enough air capacity so you may need to upgrade, or add a second in parallel.
  2. I ordered in November and had them within a week. Very nice well made product. I'm going to use them as tug straps.
  3. I've had two clutch problems using car oil in an XR and a CRF250X. Any clutch problems with the Mobil1 0W-40? There are many Mobil 1 oils so is your choice a MC oil?
  4. There is a snap ring that holds the seal head in place. Press the seal head into the shock a bit and you will see the snap ring. Pry it out of the groove with a small screwdriver.
  5. I've had a variety of XRs beginning in 1980 and I have an X. It is indeed a next gen XR but based on a MX chassis and engine. Steering is a bit slower than a XR but high speed is better. Engine seem to have a broader power band than an XR. More HP than a XR400. Has a counter balance shaft to lessen engine vibration. Rubber mounted handlebars. Nice 5 speed tranny. Far better suspension but may need revalve for slow technical work. Add the biggest Steahly flywheel, it transforms the engine for trail riding. JD Jetting adds power and throttle response. R header and aftermarket exhaust take away bottom end, which is why I switched back to stock. A minor exhaust mods adds bottom end. Auto centrifugal compression release is nice; kick starting is easy, it helps avoid brake stalling the engine, and makes bump restarts a non event.
  6. All of the "T" oils are clutch compatible, I've used the old T 15W-40 for many years in XRs. Engines and oils have have changed over the years because of mileage requirements and protecting catalytic converters. In my X I use synthetic oils in both sides; Motul 300V in the engine and Valvoline Dextron VI in the tranny.
  7. Bill Nye "The Science Guy" is a buffoon who wear bow ties like the clown he is, Frank Nye is the engine guy.
  8. Just me but I hate the hassle of mixing gas, and keeping track of the contents of several cans. Grabbed the wrong can once and had to rebuild my chainsaw.
  9. So many variable between rides, engine builds, etc, that any noticed temp differences wouldn't be valid. I had a Vapor on the bike for several years so I was familiar with cylinder head temps during my typical rides with the stock and Powroll engines. During breakin of the original Powroll build cylinder head temps steadily declined during breakin. One thing that has surprised me with the XR200 engines is the lower than expected oil temperatures, they seem to settle in the low to mid 200F range. I don't check while riding, but when stopped I'll glance down at the dip stick thermometer. I have observed cylinder head temps as high as 420F during long climbs in the mountains on a hot day. From dyno work I know bad things begin to happen to air cooled engines when the temp goes above 400F, but that is WOT and not at lighter loads like trail riding.
  10. A 428 chain is about 2mm wider than a 420 chain. 428 also has slightly larger rollers. Check out and
  11. If the countershaft has the course splines like the XR/XL185/200 then use a XR185 sprocket. The XL125/185 also used a 420 chain. A 520 chain has a 5/8" pitch, a 420 chain has a 1/2" pitch so I'm puzzled how you changed a 520 sprocket to a 420.
  12. Yes I did but I'm now back to Redline, but next oil change I'll go back to the 300V. I liked the clutch action better with the Redline but the testing in the link shows Motul 300v is better. And I do have a Megacycle cam, and they are very specific on assembly oil and lube oil. You can buy 4L of 300V for $66 on Amazon.
  13. The last time I was inside those carbs was more than a decade ago. I do see that there is no O ring on the part fiche, but Honda only sells the O ring and washer in a set with the mixtures screw. So the part fiche picture is inconclusive. The 250 carbs are larger than the 200 carb, good for top end, bad for low speed throttle response. But with the progressive twin carb setup you will probably not notice the reduction in low speed throttle response. On jetting; these engines were not jetted correctly from the factory, Honda did some adjustments for 85 and then went to single carb in 86. The lean jetting caused overheating and engine damage and aftermarket rejetting helped. You'll notice in the last two columns of the chart that as the pilot and main jets increased in size the needle clips and mixture screws went leaner. Air flow will be slower thru the 250 carb(s) than the 200 so less vacuum to pull gas from the float bowl. Pilot jet affect starting and idle, with its affect taper off to near zero by 1/8 throttle. All of the jetting circuits have overlap so jetting becomes a challenge of balancing changes in one circuit against another. Since you will probably not change the needle or needle jet your option are pilot, main and clip position. I would use the mixture screw position as an indicator of pilot jet size. Main jet can be checked by throttle roll off at mid rpm; power reduction should be smooth, increase in power indicates small main. Jets for PD carbs are available but the needles probably not. Jet R Us does sell needle jets and Kehin needles but no Honda unique needles. Keihin needles have a 3 digit code marking, Honda needles 4 or 5 letter/number combination. OEMs often use multi tapers needle on 4Ts. KEIHIN Tuning: 1/16 – 1/4 throttle; change the needle diameter. 1/4 – 1/2; move the clip up/down, or change to a needle with a different D1 dimension 1/2 – 3/4; change taper Jetting for North America: 84 200 85 200 84 250 85 250 mod 84 250 Main pri carb 98 98 108 108 102 Main sec carb 95 98 105 98 108 slow jet 42 42 45 45 50 Pilot screw 1 3/8 1 1/8 1 1/4 1 1 Needle clip pri 4th 4th 2nd 2nd 1st Needle clip sec 3rd 3rd 2nd 2nd 1st Here is a TT thread on 84-85 RFVC XRs: There may be others in other XR250/400 forum or the jetting forum.
  14. At the same time I also had a Husky CR400 and there were interesting differences between the two. In dirt the BSA was as fast as the Husky, on pavement the Husky was faster. On a slick track I could beat any 400 2T to the first corner. One event had the start on a grass field, so I started in third gear, wife says I was carrying the front when I shut down for the first corner. The CR400 was a lot lighter and more agile so I preferred it for trail riding, it was also almost a tractor after I added a small bleed port to the exhaust.
  15. Oils have changed a lot over the years but so have engines. OEMs design engines to survive in their intended environment, and that includes the quality of lube oils at the time. Buick was using roller tappets in the early thirties but later went back to flat tappets. When you look at the range of boundary lube in the above link, and the oil brands it becomes apparent that production engines don't need the high performance oils. However air cooled engine do run a lot hotter than water cooled so better high temp performance may be needed. One interesting outlier in the data was an aviation oil for air cooled engines. A lot members of this forum are using high lift flat tappet cams and they definitely have lubrication issues. Megacycle recommended that I switch to Motul 300V oil, and it was rated outstanding oil in the above link.