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Post by rafa73 on Aug 8, 2016 9:07:14 GMT -5
Hello Everyone,
And this post is about.... hesitation!
I'm joking about it because I've found so much about this issue here, that I'm sure some of you can't stand talking about it anymore.
I’ve read about several tips, involving carb ultrasonic cleaning, petcock and air filter element check, ignition timing, cable, float level, AP and PV adjustments, main and secondary jets replacement, etc.
But, of course, I don’t expect my bike to have all these problems at the same time, so I’d like to start with the checks and repairs that are easier to be done, and don’t require parts.
My bike is a 1976 A model, with 17000 miles, quite original and nicely kept. I bought it in the US a couple of years ago.
It starts and idles fine either cold or hot. I use the choke for cold start but I switch it off a few minutes later, as soon as the temp gauge needle starts moving. It has good power and does not smoke. It normally runs at mild temperature, the radiator fan will switch on only on hot days.
Hesitation occurs always at the same point of the throttle, and that is when the S logo on the grip is at the vertical position. I only happens in the first twist after idling, that means, once it overcomes the hesitation, I can pump the throttle several times, and it won't happen again, until I let the engine idle again. And apparently it happens more at higher RPMs, that means, if I skip the 2nd or 3rd gear and go straight to 4th or 5th gear, there is no hesitation. It only happens when riding, with the bike in movement, under load. Riding with the choke on does not change anything.
Before I read the older posts, I have removed the carb, cleaned it (not ultrasonic) and replaced the pump diaphragm, but nothing changed.
Any clues?
Thanks in advance,
Rafael, from Brazil.
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Post by wayne on Aug 9, 2016 2:32:10 GMT -5
Hi Rafael, There is no point giving you any ideas as we all know what the hesitation is. The bike is briefly leaning out as it changes from the primary to the secondary throat as there is a slight lag occurring before enough fuel is flowing to match the increased airflow.
While it's true that the bike can run without a hesitation, it's also true that it can be very difficult to get it to that point.
I strongly suggest you buy a $10 #100 primary jet and swap out your existing one with the bigger one. It takes less than 5 minutes to do this. It'll significantly improve or cure the bike in most cases and let you enjoy it for as long as you care.
One day in the future you can pull the carb, check that all the internal and external brass plugs are still in place, ultrasonically clean it, set the float very accurately accounting for any variation in the float bowl gasket thickness, check your air filter material, align your PV and AP and for fine tuning, set your timing.
But until you're willing to do that ultrasonic clean, buy the big jet.
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Post by rafa73 on Aug 14, 2016 9:10:24 GMT -5
Hello Everyone,
Thank you Wayne for taking your time to reply my post, and for sharing your expertise with me.
I took your advice and bought the #100 and #110 jets. I was able to find them in a local parts shop, they were being sold as parts for a Honda 450, at US$10 each.
I first installed the #100 jet, and the hesitation got a little better, there was maybe a 20% improvement. And running with the choke ON made it even better, maybe another 5%. With the original #90 jet, it did not use to make any difference.
Then I tried the #110, but I could feel that the engine was running quite rich, and starting and idling were not as smooth as before (and they were very smooth and made me very proud).
Well, even with the progress achieved with the #100, I'm not happy, riding my bike is still an unpleasant experience, unless I shift early and keep the RPMs low.
But I'll try every tip that I found in this forum, and if they don't work, I guess I'll make of it more a conversation piece, than a real motorcycle.
Thank you, if you have any other ideas, please let me know, and if I find out something interesting, I'll let you now too.
All the Best,
Rafael.
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Post by wayne on Aug 14, 2016 22:51:46 GMT -5
Well Rafael if you've found that the bigger jets only made a token difference and the bike is still too unpleasant to ride, then I would suggest that a few other things may be out.
I'm not sure if you've checked the PV timing. You never know, someone could have screwed it way out of adjustment fiddling with the carb. There is a way to time it without the protractor but it's a bit hard to explain. It needs to be 35 degrees or pretty close to that. Next check the Accelerator Pump. I have found that bikes will run hesitation free with the AP at 35 degrees also but I seem to have had more luck with the recommended 28 degrees that the factory later changed to.
Check that these fundamentals are about right. Protractors do come around on Ebay sometimes and at worse I can try to explain how to do the PV without one.
Let us know if you've found these to be about correct or not and how the bike runs once you've adjusted them.
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Post by kanonkopdrinker on Aug 15, 2016 1:36:41 GMT -5
Drastic steps I guess, but fitting the SU carb to my RE5 removed all traces of the hesitation.
David
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Post by timpa136 on Aug 15, 2016 18:47:26 GMT -5
Hello Everyone, Then I tried the #110, but I could feel that the engine was running quite rich, , I'm not happy, riding my bike is still an unpleasant experience, unless I shift early and keep the RPMs low. But I'll try every tip that I found in this forum, and if they don't work, I guess I'll make of it more a conversation piece, than a real motorcycle. Being able to determine an over rich stumble goes a long way to dialing in this carburetor, keep the faith. Tim
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Post by rafa73 on Sept 25, 2016 6:46:58 GMT -5
Thanks Wayne, David and Tim, for the extra advice. I'm sorry I took a while to reply, I thought I had signed up to receive notifications about this post, but I hadn't, and I had not seen your replies until today.
Last week I took my bike to a carb expert, he's been doing this for 30+ years. I first met him in 1990, and he's helped me a lot in the past with several different carbs. He is a car mechanic, but he accepted the task. I just had to tell him what it was about little by little:
it's a carb; it's a Solex; it's used on Land Rovers; but it's on a bike; that has a rotary engine!
Well, in the end he got all excited with the challenge and promised to solve the problem. I should hear from him next week ad I'll let you all know.
You know, sometimes all you need is to look at the problem from outside the box.
Thanks again!
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Post by rafa73 on May 19, 2019 13:15:57 GMT -5
Gentlemen,
I'm back to this thread, almost 3 years later, to tell you that my RE5 is now hesitation-free.
I didn't take 3 years to fix it, it's just that I felt kind of hopeless, and had other projects that gave me more motivation.
I followed the technical advice given by @jess, and it worked just fine. Take a look here:
All it took, mostly, was a good ultrasonic cleaning, and do it all by the book.
Thank you @jess for sharing your expertise and also for your moral support.
I had plans to sell my bike, but not anymore.
Rafael.
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Post by jm0406 on May 19, 2019 13:30:58 GMT -5
That Jess guy, He seems to know everything. Jeff
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Post by wayne on May 19, 2019 23:16:47 GMT -5
Congratulations, the Ultrasonic is the essential component and you've once again proved it can be fixed. It's not "a characteristic" of the bike that you "just accept" as I've heard some say.
Was the advice given @jess any different to what I said in the second post of this thread? I'd like to know what I'm missing:
"One day in the future you can pull the carb, check that all the internal and external brass plugs are still in place, ultrasonically clean it, set the float very accurately accounting for any variation in the float bowl gasket thickness, check your air filter material, align your PV and AP and for fine tuning, set your timing.
But until you're willing to do that ultrasonic clean, buy the big jet."
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