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vanrooster Topic :   Air cutoff valve on 1977 XL350 My 1977 XL350 has been having a strange problem that I believe is rooted in the carb.  I've long suspected a vacuum leak, but I've been unable to locate one.  When warm, the engine doesn't want to come down from high revs.  Even if I bring them down using the compression of the engine on deceleration, the revs still jump back to 3K or so once I put it in neutral and wait a couple of seconds at the light/stop sign.  When first started, it idles fine, maybe even a little low - some adjustment needs to be made there for sure.  Also, when revving it in neutral from idle, it seems to jump from 3k - 4 or 5k with only the barest hint of twist...  the spark plug is a nice healthy tan color, if that matters... Anyways, while looking at it today I pulled off the air cutoff valve and saw that the O-ring between the cutoff valve assembly and the body of the carb itself was out of its recess and a little squashed on the side.  This O-ring doesn't sit in a round recess, rather it has a lobe at the bottom of it.  In my Clymer manual on Honda Singles 69-82, it's labelled with a number 21 on the exploded view of the carburetor for 1977-78 XL350s - if that means anything to you out there.  Does anybody think that this could the culprit?  I've so far been unable to source the original O-ring, though I've got one that might work (the bike is currently at a friend's shop)... in the case that this is NOT the culprit - or even if it is - is this really a necessary part?  Other sources I've found on the internet say that its main function is reducing backfiring... Any further ideas?  This has me and the two much more experienced mechanics helping me a little flummoxed...  I'd post some pictures, but I have no camera :( Thanks, Sam 11/20/2009 20:39:59

sixdayguy Topic :   74 honda crf250?? This is a another project that I dont have time to finish. It is a 74 honda xl175 engine. I hade a 74 cr250 and a 74 xl175 frame, when I compared these frames I was surprised how similar they were. I decided to cut up both frames using the engine cradle out of the xl frame with the rest of the cr frame I also replaced the top tube & down tube with some good cro-moly tubing. I also fabricated a box section cro-moly swing arm for it. The frame still needs a little more work but will be very trick when done.  I have a new powel big bore piston & a new sudco mikuni carb. A bunch of 74 cr parts for it wheels, forks ect. Make me a reasonable offer if you would like to take over this project? Thanks, John sixdayguy@yahoo.com  11/20/2009 08:39:22

sixdayguy Topic :   74 honda xl 350 engine&champion frame for sale I have a very clean low mileage 74 honda xl 350 engine & a champion side port mx frame&swing arm. I was going to build up an AHRMA MX bike, but I just dont have the time. So if anyone is interested in this project let me know. I would sell it very reasonable, make me a offer. Thanks John.  sixdayguy@yahoo.com 11/20/2009 08:22:57

BikerMike Topic :   Re-jetting XL250 after air box removal Hi, I have removed the complete air box / filter, and replaced it with a filter that mount direct to the mouth of the carb. Can anybody advise me if I need to fit larger jets. Regards, Mike 11/20/2009 04:22:26

brettzilla Re :   replacing wiring harness.  thanks i'll do my best. 11/19/2009 21:40:39

350s Re :   Running CDI direct from battery Kyle, Had to stay home. Played to much last summer, got to work and pay for it now. The young pro classes looked big but the others didn't seem to have very many in a class. OK Russ, your welcome. Pat.  11/19/2009 20:14:49

Russ447 Re :   Running CDI direct from battery  Thanks for the replies.  All wires are re-conected at the moment and I'll go back to the drawing board.  I'll post up whatever I end up with. Russ 11/19/2009 16:59:52

Kyle44x Re :   Running CDI direct from battery Hey Pat... Thought I might see you last weekend at Lincoln. Did  you go? Kind of a slick track, like polished glass by the end of the night. I could have used some ice screws in my front tire... sure spooked me when it started sliding! Huge turnout though. Take care, Kyle 11/19/2009 11:42:37

350s Re :   Running CDI direct from battery There ya go. Trade and you both have the correct set up for what you like to ride. Freight might get in the way[cost]. Pat Orman. 11/19/2009 10:21:08

Kyle44x Re :   Need tuning help on project racer. Gride2, Nice job on the bike! I'm kind of new to these xl/xr hondas, but I'm working on a project racer and really like what you did. Do you live around the KC area? I saw you raced the vintage mx in KC... I'm in NE Kansas. Kyle#44x 11/19/2009 09:58:10

Kyle44x Re :   Running CDI direct from battery I run a lightened flywheel and the the ignition is lightened up as well... I don't know if its feasable for you to do, but my crank end was converted to use a motoplat ignition. Very light and likes to rev. Kyle#44x 11/19/2009 09:38:28

Swiss Re :   DOHC 161cc LSR project update What kind of speeds have you seen with your engine mods so far?  What rpms will it run in your testing?  Any glitches or problems with the power curve? Swiss 11/18/2009 21:56:43

orcabee Re :   replacing wiring harness.  they're all color coded.......remove/swing open the sear. Shut off gas, remove hold down bolt, remove battery cover.........most important, have a schematic. There are some wires in the harness that are not used. 11/18/2009 21:26:26

350s Re :   Running CDI direct from battery Those CDI's are AC current not DC. The XRmodel had the lightest rotor but not a great difference. I've adapted one of those ignitions for pit bikes[rotor is only about 50mm in dia.]and a couple other types onto earlier XL's but takes a "bit" of work. Maybe PVL makes a CDI for those as the 500 is the same ignition. Plug the white wire back in, don't remember what it does[maybe low and high speed?]but the Ascot's had a blue and white wire[same or similar ignition]and needed both. Would run, but wasn't right.  What you want is one of those old Honda XR250s crank kits. Lightened[porkchopped]flywheels, rebalanced including the counterbalancer weights. I think you could get a lightened rotor also.  Offered a piston and valve fit too with contingency money paid in MX etc. but nothing for iceracing-da!!it. I'll quit rambling, Pat.    11/18/2009 21:00:44

brettzilla Re :   replacing wiring harness.  how do i know which connections go to which plugs? i mean, at the front end i got the light, horn, turn signals, etc. how do i know which one to plug into which part of the harness? oh ya, and after re-reading your answer, i saw that you already answered my question about dismantle. tank only! 11/18/2009 20:08:03

brettzilla Re :   replacing wiring harness.  thanks it sounds pretty straight forward. is it easier with the seat and gas tank removed? or is it a side access job? 11/18/2009 19:52:53

Russ447 Topic :   Running CDI direct from battery I know it isn't strictly speaking an XL, but I am a bit stuck and thought this would be a good place to ask. I have a CB250RSA that I use as a sand racing bike.  As it is a race bike I have taken the charging system/battery off the bike.  The alternator output originally had 3 x yellow wires to the charging system - now junked - and a white and a blue wire direct to the CDI.  The bike has run fine like this for a couple of years. I would like to run the CDI with battery power as it means I can lose the stator/flywheel and the associated weight.  It also means there is one less moving part to go wrong. I established that the bike would run fine with only the blue alternator output wire connected to the CDI so what the white wire does is a mystery to me.  (The pulse generator wires and CDI earth are still in place, the ignition switch wire is connected to a lanyard cut out.) I connected the blue CDI input to 12v DC battery (the RS is 12v) = one spark only. Re-connected the blue CDI input to alternator power = no sparks. Connected a different CDI unit to the alternator power (blue wire only) = sparks again. So I have killed 1 x CDI and am not much wiser.  The things I had read previously indicated that getting enough power from a battery to power a CDI would be a problem - I guess not in this case.  If any one has any ideas they would be appreciated. Thanks, Russ 11/18/2009 17:13:51

English Ph Re :   Stator check http://www.carlsalter.com/motorcycle-manuals.asp Heres a great link for manuals for loads of bikes, all free. It lists the XL500 which could have a similar set up, Phil 11/18/2009 16:48:26

English Ph Re :   Stator check http://myfiles-express.com/search.php?search=free%20honda%20xl250%20service%20manual Try this for the manual. As Swiss and Pat say, make sure the battery you use is healthy, i.e.  around 6.5 volts. One sure way of killing the reg/rectifier is running with a duff battery over a period of time. With a good battery and every wire connected as it should, you can do a simple voltage check across the battery. You should be seeing an increase in voltage over the batterys. The sytem is quite basic, so you will need to rev the engine past 1500rpm to see a good increase. My money is still on the reg/rect unit. Pat or Swiss may know, but is it possible to swap the winding connections for the lighting and charging? If the coils are the same number of turns etc? This could eliminate the stator. Good luck. 11/18/2009 16:43:21

generators Re :   DOHC 161cc LSR project update 2010 SPEED WEEK - 8th - 12th March 2010. Swiss. There's going to be 2 tracks next year (if we can get the man power to set up etc ) the new track will be 3 miles total, with 1 mile run up, but, GPS speed logging only, and no new records can be set using this track. The idea behind the 2 tracks is to lower the wait times, and let everyone get a run. Tiny 11/18/2009 16:37:19

Latest 10 Hot Threads   (threads containing 10 posts or more)

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