1975 Yamaha DT175 bogging down...Need help

[chadwic10]

I am currently repairing an old 1975 DT175. I have just got the bike up and running but as I accelerate the bike seems to bog down. I've tried checking everything I know how but have had no luck. Any help is greatly appreciated.

[VAL]

First of all I see that you have already started with asking about spark plug gap (good start). You can ask at the place you bought your plug, what the gap should be for the plug. The gap is determined by the plug design rather than one bike uses one gap and the other uses another on the same plug. (Correct me if I am wrong anyone out there).
Second, could you be more specific on the bog, is it just flat at mid range with no further exceleration, can you rev it up in neutral?

[chadwic10]

Thanks for the info on the plug. The best way I can explain the bog is as I start riding the bike seems to run fine but as I accelerate and really pull on the throttle the bike just looses power as if there were no fuel. I have check the fuel line to make sure fuel was getting to the carb but all was well. I the bike will actually climb in speed but you have to find where the sweet spot is in the throttle for it to gradually speed up. If I pull back on it too fast it boggs down and will stall if I don't let up on the throttle.

Let me know if this explains any better

[chadwic10]

Sorry.... you can rev it all you want in neutral or if you have it in gear with the clutch in.

[MXtras]

Lots of things it could be.

Fresh fuel?

Clean air filter?

How's the compression?

Sounds to me like your compression could be a culprit.

Scott

[VAL]

My IT 175 had the same problem.

Three problems:

bad pick up coils, plug gap and too rich on the main jet.

The coils kept from running at all the jets help alot but still stammered on the top end. Check my gap and it was way too big. Runs great now.

[chadwic10]

I'll take a look at these and see if that helps at all.

[MXtras]

Considering VAL actually has one of these, take his advice before mine.

Scott

[chadwic10]

Ok. well I tried a few things. One I check the air filter and it seems to be pretty gunked up. I also my mistake found out that the bike will run at the high speed/full throttle if I pull the choke out but once I slow down and come to a stop it cuts on me.

I'm not to sure on the Pit up coils and where and how I am supposed to check these.

Thoughts?

[DOGBOY]

you are running lean. by turning the choke (on) you are giving it more fuel hence running lean.
at wot it is getting more air than fuel. by closing the throttle down you are closeing the air to richen it up, hence running lean.
i would verify you have a 160 main jet and the needle clip is in position 3. both of these are factory stock.
and of course you may want another o-ring for the needle jet just incase you tear it or it is in sad shape when you go to put it back together. oh yea, cleaning the carb is also very good insurance to get it running properly.

dogboy