project r90/6 wont start -- help needed

[pleather717]

Hello, new to forum i am trying to bring a 75 r90/6 back from the dead. the old " it ran when i parked it 10 years ago" kind of bike that has taken up my few hours of free time on weekends.

here is what i have done:

new starter relay. new plugs/wires. fresh oil. fresh gas. new points, new condenser. timing adjusted statically to "s" mark. points properly gapped. fully charged battery.

bike will turn over and chuff but will NOT start unless i spray a touch of starter fluid into carbs then it will run for a few seconds and die no matter what throttle or choke manipulation i try. i have tried to reset carbs to specs per haynes manual ie turn idle screw in and back off 1 turn etc.

shorting the plug to the head shows a fairly weak yellow spark

any thoughts?

could it be the 40 year old coils?

any help greatly appreciated i love the site it has been very helpful

[Duane Ausherman]

"..............but will NOT start unless i spray a touch of starter fluid into carbs then it will run for a few seconds .........."

This is the key information that I would first pursue. Forget starter fluid if possible. For a second or two it is OK. Now I would remove the plugs and squirt in a couple cc of fuel, replace the plugs and start it up.

Are you in a cold garage? You might put a heater under it overnight. Obviously you don't want that forever, but it might help it run well enough to assist.

You are running out of fuel. I would not worry about resetting the carbs to spec, but check for clogged up jets and air intake leaks.

Examine the spark in the near darkness to see the true color. Keep us informed with your progress.

[Airbear]

Welcome aboard pleather.
You don't indicate that you have played with the carbs yet or checked your valve clearances.

The carbs are simple enough to pull apart, check and clean. It is likely that there will be blockages in the tiny passages associated with the idle circuit. I have found that the easiest way to pull the carbs is to loosen the hose clamp screws at top and bottom ends of the tube on the air cleaner side, similarly the clamps on the head side, then pop the carbs off. Rotate the carb and you will find that the throttle and choke cables will be easy to remove. You can then set yourself up comfortably at the workbench (kitchen table in my case) to do a bit of investigating. Some suitably potent cleaning solvent, compressed air and some nylon fishing line should help to clear the tiny passages. Check the diaphragms for holes by holding them up to the light and stretching them. Remove all jets and clean them. Pull the enrichers apart and check them, but don't get the parts mixed up between right and left carbs. If you find damaged o-rings a carb refurb kit is required. Have fun.

O, and while you have the carbs off it is the perfect time to do a compression check.

ps: Yes, could well be the 40 year old coils. New 6V Bosch coils from a VW shoppe made a big difference to the sparks on my old girl - instant change from weak yellow to fat blue sparks.

[pleather717]

thanks guys,

yes i have cleaned carbs and installed news o rings and gaskets, valves have been checked and rechecked, are correct settings for intake and exhaust. when i push carb diaphram up it slowly comes back down, choke hole in float bowl is unblocked. this was my first airhead carb cleaning so there is a chance some tiny hole is still blocked - i used the dunk method of carb cleaner. will use air compressor and fishing line.

i live in central california so a cold garage is not really the issue.

just went into dark garage and sparks are yellow for sure.

getting close, when i picked this bike up it was in need of some work for sure. but there have been quite a few head scratchers with this one.

[jagarra]

Since you say you have gone through the carbs, have you looked at the petcocks and fuel line. If you pull a line going to carb is it gushing out or??? Sitting that long no telling what has sunk to bottom of tank, and to petcocks. The filters inside on the input to the petcocks could be blocked.

[pleather717]

jagarra,

fuel is getting to both carbs, the float bowls fill. tank is in pretty good shape. i will pull petcocks and clean as well.

[Duane Ausherman]

Don't pull and clean the petcocks just yet. First do proper and logical diagnostics. Don't do a shot gun approach. You can and you may find it, but you might spend a lot of wasted time and money.

Just measure the flow rate out of the petcocks first.

Are you using articles on the web to do this stuff? Everything that you need to know is already on the web. Save time by not waiting for us to type it again, just do a Google search.

[tsa]

bike will turn over and chuff but will NOT start unless i spray a touch of starter fluid into carbs then it will run for a few seconds and die no matter what throttle or choke manipulation i try.

So It doesn't get enough fuel to run when cold . . . . , are you sure the "choke"s (actually separare enrichener carbs) were reassembled correctly? It is possible to replace the rotating disks inside them the wrong way around. Easy to check.

[jagarra]

I have experienced the same type of symptom's before. I had to take carburetors apart and make sure all orifices were clear. I use a wire like safety wire to push through every opening. Clean with carb and choke cleaner and compressed air.

I just went through the process of resurrecting a 50 plus year told truck that had sat for more than 6 years. The entire fuel system including gas tank had to be replaced or rebuilt. Evaporated fuel left in the system leaves a residue that hardens and blocks the passageways in the carburetor. Your issue sounds like the fuel is not getting atomized and pulled into the intake port.

[Ken in Oklahoma]

. . . Are you using articles on the web to do this stuff? Everything that you need to know is already on the web. Save time by not waiting for us to type it again, just do a Google search.

Duane and I have an ongoing disagreement on this. Asking and answering questions for us (most of us anyhow) is satisfying and is the springboard for many interesting discussions--some of them actually relating to the question. I guess I feel pretty protective about this forum. I have learned practically everything I know about airheads through this very forum. But more important than technical knowledge is the social interaction. Through this forum I have developed several wonderfully satisfying personal friendships. How much is that worth?

The advice you get here is what it is. This is even true, by degrees, on the rest of the internet. Consider the requirements for getting on the internet. That would be money to buy a domain and computer savvy to make the domain function.

It is completely OK, perhaps even advisable, to check around on the internet for what you want to learn. But to boycott a certain segment of the internet, i.e. forums like this one, is to short change yourself from a significant pool of information and advice that is well worth considering.

Editing: To be clear, I'm not promoting going to Boxerworks only.

Ken