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O/T: 1978 Honda XR75E carb adjustment?

M

MeAnthony

Member
I just picked up this bike for my kids; it"s a small dirt bike. It won"t start with the kickstarter, but will fire and somewhat run if you pull it down the road. I plan to clean the carb and points tomorrow. At the same time I"d like to make sure the carb is set properly. However, I can"t find any info on how to set it and it"s been too long since I"ve messed with something like this to recall.

Any suggestions or information is appreciated.

Thanks for your time,

Anthony
 
Talk to a Honda dealer. The same basic engine is still used in the CRF80 and CRF100 models. It's a bullet proof engine. I had a 1976 XR75 that did kind of same thing. The first time I think it was the coil but I'm sure the other time it was ignition related and the carb wasn't the problem. Take the side cover off and see if there's any corrosion inside. Probably need an impact driver for the phillips head bolts. Make sure you have fresh gas as well. Dave
 
Also see if there's a plug or screw to drain the carburetor bowl, might be water in there. Just a drop will mess it up sometimes.
 

Simple repair.

Pull tank off bike and remove valve from bottom , there is fuel filters on the valve.

Clean with "Gumout"... it works best.

Pull carb.

Remove fuel bowl.
In the bottom you will see the main jet and a pilot jet.
The pilot jet has a flat hesd screw driver face.

Remove it and make sure it is clear, it will be a "VERY" small opening , nothing but gumout .

The next important part is the air screw.

Turn it in counting the turns , then remove it . Use the gumout threw all the carb holes.

Reinstall the air screw , it should be around one and a half turns out.

Put it back together and go.

The carb has "3" metering circuits.

Pilot jet = starting and off idel throttle responce.

Needle= mid range throttle.

Main jet= wide open.

Any questions just call.

I will be at a tractor pull on Sunday so keep calling because i might not hear the phone.

Jim 586-524-0371


P.S put a fresh "brand new" spark plug it it as well. Try and get away from that NGK crap.
 

You do not work on this stuff on the scale i do.

If you soak a NGK in fuel it is all done. Burn it with a torch or what ever you want to do , it still won't fire correct.

Here in Michigan the snowmobile season is about to get underway. You would laugh at the number of times fresh plugs cure a problem.

I like and have had great results with Autolit plugs in things that number wise transfer over.


I only use Autolite in my toys.

The NGKs do work well in the old road bike , but keep in mind there four strokes as well.

I playing with a 1974 Honda CB 550 four cylinder right now , building a bober.
 
I'm in MI also, about 20 minutes south of Jackson, right outside the big town of Moscow. Maybe we're almost neighbors?

Thanks for the great info. Other things have come up, not sure I'll get to it today now, but definitely as soon as possible.

Y'all have a good weekend!

Anthony
 
I used to race motocross and know a few of the shops. NGK's were never a problem. I'd say it was a safe bet that 95% of riders ran NGK plugs. The splitfire plugs were the worst. They cost twice as much and fouled almost just by looking at them. One of the fastest pro's dad owned the Honda shop and he put a splitfire in his bike. Fouled on the starting line. Luckily it was before the 30 second board, so he alerted the starter and had time to put an NGK plug in. He's been racing for over 25 years and never had a problem with NGK's. Dave
 
Cleaned plug and carb. It won't start with the kicker. It will fire up by pulling it down the road. It only runs decently in the mid RPM range. Low end works, but not very well. High range RPMs lead to misfiring and stalling.

Of the two adjustment screws on the right side of the carb, one is located under the throttle valve slider. I assume this screw only sets idle RPM and the other screw is air/fuel mixture?

I set both screws to 1 1/2 turns out. Adjusting more on either one doesn't seem to make any difference.

I should check the compression also. Where should that be? I'd guess around 100lbs or so?

Thanks again,

Anthony
 
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