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Where Do I Start?: Starting Issues with 1976 MR175 http://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=4782 |
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Author: | chris_97 [ Thu May 18, 2017 5:50 pm ] |
Post subject: | Where Do I Start?: Starting Issues with 1976 MR175 |
I have a 1976 MR175 that has been under maintenance for a couple months. I will list all that I have done below: -Replaced the carburetor with a brand new Mikuni VM28-49 Round Slide (28mm) -Replaced the old throttle cable with a new CR125 cable -Replaced the handlebars -Replaced levers, mounts, and added new mirrors -Replaced the pawl spring on kick starter -Changed oil -Replaced old fuel with fresh fuel with 32:1 ratio -Replaced the fuel line -Replaced spark plugs A week ago, my bike would run and idle just fine. Now, it doesn't even act like it wants to start. The gas tank is a little rusty on the inside. I have adjusted the carburetor and tried starting with the choke opened and closed. I do not know exactly how much compression I have, but when I kick, I get some pretty breathtaking compression strokes. My spark plugs have spark. My airbox does not have a filter in it, so it is getting plenty of air to the carburetor. I cleaned my carburetor and the hoses going to the head and the airbox. I do not know where to start with this bike. Where should I look? I would appreciate any advice or information! -Chris |
Author: | rayivers [ Sat May 20, 2017 2:36 pm ] |
Post subject: | Re: Where Do I Start?: Starting Issues with 1976 MR175 |
Chris, From your list, it seems you've done all the easy stuff - which often works - but having been there many times before, here are several more items which should at least give you a better idea of what's wrong by process of elimination: 1) check compression (with a gauge, not your foot - see below) 2) set ignition timing (try setting points gap to .012") 3) clean exhaust spark arrestor (just ahead of tailpipe section; you'll need to remove tailpipe insert first, then I used long ultra-coarse pipe cleaners from a pipe/tobacco shop) Cheap MC-friendly compression gauge: https://www.walmart.com/ip/Equus-3612-I ... 3=&veh=sem Ray |
Author: | chris_97 [ Thu Jun 08, 2017 10:19 pm ] |
Post subject: | Re: Where Do I Start?: Starting Issues with 1976 MR175 |
Ray, Sorry for the late response. I have finally gotten around to looking for all possible issues. I have spark going to my brand new plugs, so I know it isn't a spark issue. I have checked my exhaust pipe and there is no spark arrestor in it. After removing my exhaust pipe, I checked inside of my cylinder and the piston, rings, and walls are in good shape. My compression is low, so I can only assume a head gasket. I guess I am unfamiliar with setting points gap on these MR's. I found the point in the left crankcase, but I do not know what screw to slightly loosen to adjust the point. I measured the gap and it is near .012" but not exact. I have a few things to do, but with that information, I wasn't sure if you would have a clue as to what could be the reasoning for my MR's failure to start back up. -Chris |
Author: | rayivers [ Sat Jun 17, 2017 5:25 pm ] |
Post subject: | Re: Where Do I Start?: Starting Issues with 1976 MR175 |
Quote: My compression is low, so I can only assume a head gasket. Really! - because unless you have plainly-visible black spooge around the head gasket area, I wouldn't assume that at all. My cylinder / piston / rings looked great through the exhaust port too, then 2 rides later the top ring snapped & nearly destroyed the exhaust port. You can rebuild your top end, or continue to chase your tail - your call. Ray |
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