Vintage Dirt Bike Q & A

does anyone know the proper timing procedure for my 1975 MR 175 ??? Thanx a bunch!

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2000 XR600R
1979 XR200R
1975 MR175 Elsinore
1987 Husqvarna 510TE

Hi ILYA
Remove the little access-cover on the left engine cover. Turn the flywheel until you see a mark "F" and another mark "T". Turn the flywheel counter clockwise until the F-mark lines up with the index mark on the cover. If the timing is correct, the points should just start to open.
You can not rotate the breaker plate as on some other Honda models. The only way to adjust the timing on the MR175 is by changing the point-gap. The gap must be within 0.008" and 0.024" when the timing is correct. The correct timing mark is equal to 20.5 degees BTDC at 1400rpm (idle) or 2.2 mm BTDC.

On your other subjects problem regarding the rectifier...did you actually test yours?
It is mounted near or on the left side of the aircleaner box.

Also you mentioned "jake-brake" on the left/angled cylinder head hole. Most bikes sold had only a 14mm plug/bolt installed there. It was meant for an auxillary sparkplug so one could switch over the cap to other sparkplug easily in the bush in case of a fouled plug. Many bikes (included my own) have a decompression valve mounted there, that was operated remotely from the handlebar by the means of a cable. It was for an engine idle shut-off or for clearing out a flooded cylinder, not as a "jake-brake".

are points supposed to open up with the flywheel still removed? cuz mine dont...

i think i will be replacing the points anyways since i am at it... so i will be playing with timing later on tonight...

i do not have a rectifier at all, somebody took it out long ago... the Y/B wire goes straight from alternator to kill switch and then to condenser and then to coil.... after doing some research, i found that Elsinore coils dont care if its AC and dont need a rectifier/regulator for the simple task of ignition... rectifier converts ac to dc and sometimes also regulates steady voltage - for the lights, and for charging bikes with batteries...

i would still like to find out how i could get a hotter coil or something... i am not too sure if i want to switch this simple old bike to a cdi system, there s more crap to deal with...

somebody else said that they used to put jake brakes into that second plug hole... the compression release valve is prolly more useful... any sources for 14mm comp release valves? and as far as putting a spare spark plug into that hole, isnt it going to get all fouled up from just sitting there and not firing?

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2000 XR600R
1979 XR200R
1975 MR175 Elsinore
1987 Husqvarna 510TE