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1980 DT175G Running Problems (US Model)


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My bike is Definitely a 175G model. Only one slot on needle - FIXED and air screw is preset. Should I try and remove the brass plug where the air screw is?? Their is a small hole in the center of the plug.

The plug on the left has been in the bike for 12 months/250 miles (NGK B8ES)

The plug on the right was installed last weekend. It probably has 10-15 miles on it (NGK BR8EIX)

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if the air screw has never been touched, ....I'd leave alone.

This idle problem may well be air related, I had a not disimilar problem, albeit it would race away. But mine would not idle properly either until I solved the airleak.

One solution to locate a leak (mine was the bottom gasket) was to make a load of soap suds bubbles and brush it all around the engine with an old paint brush whilst its running, any bubbling will locate the leak.

(A similar method is used to spray WD40 on the crankshaft seal as mentioned before)

Might be worth a go....its only soap suds!!! and you'll clean your bike at the same time!

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NEO - thanks for the soap sud test idea. I just spent 10 minutes checking it over. I think it may have a bad exhaust flange gasket as I did notice a few tiny bubbles coming from that area. I nipped up the bolt a little bit more and the bike tried to idle. I am going to order a new gasket. Thanks again.

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yeah I was kinda thinking there may be an air mixture screw under that anti-fettler cap

so tell us about the carb and to what degree you have cleaned it, did you completely dismantle it and ultrasonic bath it, did you spray carb cleaner down every orifice, did you blow compressed air through them????

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The carb has been completely disassembled on at least four occasions. Each time it was disassembled the body and internals were soaked in carb cleaner overnight. I blew everything threw with compressed air before reassembly.

Update - I just took the bike for a six mile spin and its is running perfectly! Zero flat spots anywhere through the rev range and its even ticking over at around 1400 rpm. Not sure if this is a fluke due to the amount of times I have had the magneto and stator off or maybe its because I nipped the exhaust manifold bolts up a little bit tighter. I am going to ride it again later today and keep my fingers crossed it behaves in the same manner.

I would like to thank all of you fellas for your very valuable help and advice. I could not have got it running without you!

The "Atlanta Fettler"

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Cheers Airhead - it really is as I love riding this little bike so much! Brings back so many memories of my youth. The fella down the street rode one to work, the kid across the street had one with all the trick bits on it. I even remember a lad racing one in our local AMCA MX club days back in 1984. He did pretty well on it too!

I hope you got your TT going without too much grief.

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  • 5 weeks later...

Probably a little late to the party...but I had a similar problem with a lumpy mid range. The trick was to lean out the needle a notch. Basically the needle tube was worn over time, causing the needle to leak ever so slightly. Leaned it out a single notch and bam it worked perfectly. Fuel economy improved markedly as well. Could be worth a try for anyone else reading this thread and not finding the solution they need.

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