disappointing...

Thanks to those who helped me with the brake thing - they're back together but I got them checked by a mech this morning before I went out, just to be sure. Seems I did good 8O

Out on the road just now for a 10-miler, still revving like crazy (about 3.5k) at idle, once warm.

New throttle shaft seals in there, carb cleaned and balanced, can't find a leak at the boots, float levels/ plugs/cable ok.

Someone posted a while ago about the rubber o rings at the idle mixture screw perishing - is this a difficult job ? Are they easy to source ?

I'm taking in so much new stuff here, it's like I'm addled. Can't find it in Haynes, CD on order.

If this doesn't do it, is there anything else it could be ?

 

What sort of bike Yepper. Helps to pop your bike model in your signature so we can advise accordingly.

The o-rings depend on the bike and carbs. Some have Mikuni which does not have the orings but most have Hitachi which do.


How did you balance the carbs? Still sounds like it's not quite right.

 

Someone just posted in the wanted, for sale section that they had some for sale.
Check it out.
Good luck

 

I'm gonna get this picture/signature thing nailed down !

It's the Hitachi carb, Hired_G -

'81 import - 750, with 650 Seca clocks, tank, forks etc

 

Surge at idle can be a real PITA to diagnose correctly. Generally caused by a lean idle condition - does your bike idle normally on start, then fail to come back to idle after blipping the throttle? If so, you're lean. Surge can also be caused by additional fuel at idle - check that your enrichment plungers are seating fully (enrichment is sometimes referred to as choke, which it really isn't on the Hitachis). There should be some play between the forks which lift the enrichment plungers and the knob on the plunger when the 'choke' is off. Mixture screw o-rings are easy, provided there are no plugs installed over top of them - look for a slotted screw on the centerline of the carb body (viewed from above), on the engine side of the carb, right next to the enrichment plungers. If all you see is an aluminum plug head (visible as a circle of slightly different material than the carb body) then your screws are capped, and will have to be drilled out (very carefully!!). If your screws are capped, its unlikely that the o-rings are the problem - not much air can get past the plug. If you need to replace the o-rings, just unscrew the mixture screw (after counting the number of turns required to fully seat it), the o-ring may have to be fished out of the screw bore if it doesn't come out with the screw. I think 2.5 turns from fully seated is the generally accepted setting. If you're lean at idle, back out the mixture screw an extra half turn at a time and re-adjust your idle to below 1000rpm. Repeat if necessary to cure the rich condition. (Check by blipping the throttle - it should return to idle fairly quickly) Its not recommended to exceed 3 turns, although I've gone out to 3.5 while playing with carb jetting. Mixture screw adjustment should not be made until you're certain your carbs are squeaky clean, particularly the idle jet and passages. Any chance the 750 motor has 650 carbs installed? Hope I haven't confused the issue for ya...

 

When i had mine in the shop the mechanic told me that it could be due to valve adjustment. He reved the bike and if the rpm's drop fast then they dont need to be adjusted but mine was slow in dropping. He also said that it could cause overheating and high iddle. Just my two cents.

Maze

 

I am not 100% sure about this.But I was having a flucating idle,I replaced my clutch cable and it seemed to sort it out.There was a kink in the line causeing the clutch cable action not to fully function.

 

Hi Lo :lol:

You've given me a lot to go for there man, thanks.

Tends to idle ok on start up. Comes back very slowly after a blip. After a few minutes of riding, if I snick into neutral it's 3k+ and will not come down at all.

Enrichment is disconnected at the moment, so not an issue I think.
I checked the float levels - they're within limits.
Carbs balanced by a very experienced friend, after thorough cleaning of jets and prepping as per Rick's posting.


No alu caps over the mixture screws, so hopefully the answer is there.

Off now to investigate the 650/750 carb issue. Doubt it though.

 

Bean - thanks for your input. But just fitted brand new clutch cable, genuine Yamaha spare... for 33 Euro.

That's about $40 US dollars. What do they go for in the US ?

 

Clutch cable for 40 bucks - now that's highway robbery ...
I have a local shop make it, they cost me $5. Of course the freaking virago 1100 broke 3 cables in 7 months, the one that was on it, then the one they made, and that broke 2 weeks ago, and I rigged a spare from the maxim pile to work. The next one they make will be free. we also can get aftermarket cables from Motion pro. One time when i was in california, when i went to cycle gear and twice their cable was wrong from my brothers FJ 600, I went with their guy to motion pro and he made it right there for us. I have since started making up cables instead of buying them. The shop made me thinner cables in place of what was on it. I now know that so I am going to make them do a thicker one even if it doesn't slide in like butter - like when did that become a criteria.
Cool.
Srinath.

 

Did you think that maybe you didn't adjust the new clutch cable correctly? If it is acting differently in neutral than in gear, that is what I would suspect!

 

Srinath, could you please explain how to create your own cables to us? I'm very interested in the process and where to source the materials from. Thanks.