SOURCE: yamaha DT175 1975 -- won`t idle back
I had the same problem recently where the idle speed was too high (3000 RPM) when the steering was pointing hard left. Here are some possible solutions to your problem. I have listed them in order of probability:
1. Choke. Maybe sounds too obvious, but if everything else is in good working order, this is usually the cause of a high engine speed at idle. Locate the choke and 'play' with it to see if this has an effect on RPM.
2. The throttle cable is tight or catching. Try loosening the lock-nut and teasing the cable away from the grip end. Don't force it too much to avoid snapping it. If it releases, check the throttle free-play is correct, and adjust if necessary. Lubricate cable at both ends to reduce any restricted movement.
3. The throttle cable is rusty. Try using a bit of WD40 at each end of the cable (handle and engine alike) and use a lubricant. 1975 is an old bike for sure, so clean & check the entire length of the cable for cracks or splits. Remember to wipe away any excess WD40 or lubricant after any maintenance. If you discover that you need a new throttle cable, these are cheap and easy to fit, and are normally available through eBay.
4. The engine idle speed setting is incorrect. There should be a screw situated somewhere around the engine case (you may have to consult the manual to find it). Turning this screw clockwise/anti-clockwise will adjust the idle speed up or down. Suggest you only perform this as a last resort.
5. Check oil. The engine idle speed can be dictated slightly by oil levels, so make sure the oil levels are between min/max on the dip-stick. Also, ensure that you are using the correct engine oil for your machine (consult the user manual), e.g. 2-stroke or 4-stroke, mineral or semi-synthetic, etc.
As I cannot guess what you mean by 'too high' when referring to the actual idle speed, I would suggest that if engine speed is more than 500 RPM above normal, it will most likely be an issue with the choke or throttle cable.
I would suggest you try finding a bike-specific servicing manual, but these are often hard to come by and can be pricey if you do eventually locate one. However, I do suggest you think about investing in the Haynes Motorcycle Maintenance Techbook: this is a generic book of bike maintenance and has loads of hints and tips that could save you loads on servicing bills. As most parts of any motorcycle are based on the same idea, much of the book answers even specific questions that apply to your problem.
Anyway, good luck !!
SOURCE: i have 1974 yamaha dt 250 enduro the bike sat
clean contacts on points with sandpaper (800 grit). located behind flywheel, will gurantee a fix. you can remove the side cover and get to contacts through holes in flywheel without removing it.
SOURCE: 1971 yamaha 175 motorcycle electrical problem
ill do a list of things that can help or be the problem.
1) Pull the coil off and wire brush down all the bare metal. then do the same to the frame where it bolted on. Make sure there is a grounded wire that bolts back onto the coil if there was one, Replace the wire end for the ground peice.
2) Pull off the spark end cap and cut the wire down a few mm until you see new wire then screw it back on. (if its NGK)
3) follow the wire from the kill switch and make sure it isnt grounding out.
4) Hotwire - find the kill switch and unplug it. if this doesnt help unplug the ignition key wiring. on older bikes it will work for ignition but not lights for the key part. if this helps you need a new Ignition barrel / Kill switch.
5) check your wiring harness make sure it isnt grounding anywhere exept where its ment to.
6) make your your engine to CDI is plugged in and has no oxide in it
7) try and find somone with a running bike the same as yours and borrow there CDI, if this helps you need to buy a new CDI or check yours for wiring shorts.
hope this helps if not buzz me ([email protected])
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