Post by wayne on Sept 3, 2010 0:43:28 GMT -5
EDIT: I see this post is still heavily read despite being 20 months old. To give feedback to any new readers, this method has become "standard" among us in Eastern Australia to cure hesitating bikes. The "cure" has worked on 4 bikes that I've been directly involved with, one of which has gone on to be cured properly and still working on the other 3. Posters around the world have also had success.
It does work to make the bike completely rideable but nothing beats a correctly set up and operating bike- ie, I'd still like to fix it using stock components. But you might find that you need Primary jets over 100 to make it effective. Also, the infamous "brass screw" that sits atop the carby and never seems to do anything. Once you do get to the large sizes, it does start to have an effect and my need some tweaking.
I believe that there are a lot of RE5's out there that have some residual hesitation/flat spot around the change to secondary carby throat. If you've tuned your bike 95% and just can't quite eliminate a trace of that problem, this may help.
I recently received this email from Paul McBurney who is a new owner of an A model. He bought it as a good runner and imported it from the U.S. to Australia. It is at the very least, an interesting possibility and I'd like to know if anyone has success with this.
Wayne
From Paul McBurney:
I have been trying to contact you to tell you of my tribulations. It's been interesting to say the least.
Jess assured me, and I have no reason to disbelieve him, that my bike was perfect before it left his shores. He is the expert. He would have had it right, or at least as right as he imagines they should be.
Following getting it here and riding it for the first time (after tracking down a sparkplug, but that's another story), the flat-spot was monumental. The bike would literally stop running at the changeover point, then suddenly resume, alarmingly, as the secondary's cut in. It made for very jerky, unpleasant progress.
I dived in to the cable adjustment immediately.
I found everything as it should be, at a glance *. I don't have the protractor, but checking things by eye, it seemed pretty right. I went through all of the adjusters including the port-valve (burning my hand in the process, of course) and nothing was untoward. It wasn't WAY out.
I then jumped back on the internet and trawled through every skerrick of info I could find and intriguing things came to light.
A posting by an owner in Holland (I think) pointed toward the flat-spot being mixture-related. He had determined through his experimentation that no matter the setting of anything else, if the primary mixture is lean, the flat-spot will never disappear.
Now... fuel here in Australia is different to fuel in the USA - it has to be, why else would there be such a difference between my bike over there to over here?
Given what I'd read, I then had a 'light-bulb' moment.
For a long time, refiners have been 'oxygenating' petrol. This means that there's more oxygen in a given amount of fuel than there used to be.
Furthermore, fuel-air mixtures in vehicles have been getting leaner and leaner. The jets required for the correct mixture in 1975 are no longer applicable for the fuel available now. You have to up the (fuel) jet sizes to get things back to where they were from times of yore.
Fuel in Oz is nuts compared to most other places. It stands to reason that trying to run an RE on fuel here (which is likely very much more oxygenated than the US) would require a re-jet.
Which is what I did.
I grabbed an old jet out of one of my GT carbs that was physically the same size and stuck it in the RE. Voila! no flat-spot AT ALL!
But, it wouldn't idle. Probably because I'd used a jet nine times bigger (87.5 to 110).
I rang ShowAndGo in SA for some jets. Ten smackers each. "Send me three", said I.
I bought a 90, 92.5 and a 95.
Long story short, the 95 works well. The bike idles beautifully and has almost no flat-spot. I feel I can tune it out completely by more careful port-valve fiddling.
Otherwise, my bike is an absolute cracker. Jess is a man of his word - he said it was nice and it is.
I had to refurbish the brakes (30 years of coagulated brake fluid in the MC meant it wouldn't release), I haven't touched anything else.
It still needs new stem-bearings and I'll be working on updating the suspension (still has original shocks, front springs and likely oil), but it's eminently rideable as it is.
I also want to quicken up the throttle. There's a nifty trick one of the GS Resources guys has come up with that does the job without ruining anything and is reversible.
The amount you have to turn that throttle to get anything to happen bugs me. I'll let you know how that goes.
Eventually I want to try a different carb, and a sparkplug adaptor. Plugs are now prohibitively expensive, even from Jess.
I haven't had to change the one out that's in there at the moment, yet.
I'm experimenting with warm-up times as well - I'm not convinced you have to let the thing idle away for hours warming up before you ride it, in fact I suspect that may be part of the reason plugs die prematurely.
Of course I don't give it a hiding from dead-cold, and I ride it conservatively whilst it comes up to temperature like I do with all my other bikes. I'm mindful that a Wankel heats and cools differently than a 'normal' engine. I've not had any issues so far.
I suspect the advice from Suzuki (and Sam as well?) about a lengthy warm-up is a bit of an arse-covering exercise.
They were obviously concerned with longevity/rotor sealing issues and persuading owners to be careful is prudent, especially given some of the lunk-heads out there.
I'll keep you up to date with any changes and/or revelations. If you have an opportunity, please give me a call and I can discuss further stuff with you.
I'll be on the RE for next year's Bathurst Rally and I'm looking forward to forming (re-forming?) the RE club down there.
And, feel free to pass my deatils on - why keep this meagre Suzuki knowledge to myself?
Cheers
Paul
* There is BTW a way to determine the port-valve to secondary butterfly synchronisation without using the protractor. You can see when the secondary butterfly is about to open by observing the movement of the limiting-plate - you can see it through the frame from the RHS. Then it's a simple matter of getting someone (like your long-suffering partner) to observe how far, or not, the port valve has opened/moved at that throttle opening.
A bit of back-and forth and you've got it sussed.
It does work to make the bike completely rideable but nothing beats a correctly set up and operating bike- ie, I'd still like to fix it using stock components. But you might find that you need Primary jets over 100 to make it effective. Also, the infamous "brass screw" that sits atop the carby and never seems to do anything. Once you do get to the large sizes, it does start to have an effect and my need some tweaking.
I believe that there are a lot of RE5's out there that have some residual hesitation/flat spot around the change to secondary carby throat. If you've tuned your bike 95% and just can't quite eliminate a trace of that problem, this may help.
I recently received this email from Paul McBurney who is a new owner of an A model. He bought it as a good runner and imported it from the U.S. to Australia. It is at the very least, an interesting possibility and I'd like to know if anyone has success with this.
Wayne
From Paul McBurney:
I have been trying to contact you to tell you of my tribulations. It's been interesting to say the least.
Jess assured me, and I have no reason to disbelieve him, that my bike was perfect before it left his shores. He is the expert. He would have had it right, or at least as right as he imagines they should be.
Following getting it here and riding it for the first time (after tracking down a sparkplug, but that's another story), the flat-spot was monumental. The bike would literally stop running at the changeover point, then suddenly resume, alarmingly, as the secondary's cut in. It made for very jerky, unpleasant progress.
I dived in to the cable adjustment immediately.
I found everything as it should be, at a glance *. I don't have the protractor, but checking things by eye, it seemed pretty right. I went through all of the adjusters including the port-valve (burning my hand in the process, of course) and nothing was untoward. It wasn't WAY out.
I then jumped back on the internet and trawled through every skerrick of info I could find and intriguing things came to light.
A posting by an owner in Holland (I think) pointed toward the flat-spot being mixture-related. He had determined through his experimentation that no matter the setting of anything else, if the primary mixture is lean, the flat-spot will never disappear.
Now... fuel here in Australia is different to fuel in the USA - it has to be, why else would there be such a difference between my bike over there to over here?
Given what I'd read, I then had a 'light-bulb' moment.
For a long time, refiners have been 'oxygenating' petrol. This means that there's more oxygen in a given amount of fuel than there used to be.
Furthermore, fuel-air mixtures in vehicles have been getting leaner and leaner. The jets required for the correct mixture in 1975 are no longer applicable for the fuel available now. You have to up the (fuel) jet sizes to get things back to where they were from times of yore.
Fuel in Oz is nuts compared to most other places. It stands to reason that trying to run an RE on fuel here (which is likely very much more oxygenated than the US) would require a re-jet.
Which is what I did.
I grabbed an old jet out of one of my GT carbs that was physically the same size and stuck it in the RE. Voila! no flat-spot AT ALL!
But, it wouldn't idle. Probably because I'd used a jet nine times bigger (87.5 to 110).
I rang ShowAndGo in SA for some jets. Ten smackers each. "Send me three", said I.
I bought a 90, 92.5 and a 95.
Long story short, the 95 works well. The bike idles beautifully and has almost no flat-spot. I feel I can tune it out completely by more careful port-valve fiddling.
Otherwise, my bike is an absolute cracker. Jess is a man of his word - he said it was nice and it is.
I had to refurbish the brakes (30 years of coagulated brake fluid in the MC meant it wouldn't release), I haven't touched anything else.
It still needs new stem-bearings and I'll be working on updating the suspension (still has original shocks, front springs and likely oil), but it's eminently rideable as it is.
I also want to quicken up the throttle. There's a nifty trick one of the GS Resources guys has come up with that does the job without ruining anything and is reversible.
The amount you have to turn that throttle to get anything to happen bugs me. I'll let you know how that goes.
Eventually I want to try a different carb, and a sparkplug adaptor. Plugs are now prohibitively expensive, even from Jess.
I haven't had to change the one out that's in there at the moment, yet.
I'm experimenting with warm-up times as well - I'm not convinced you have to let the thing idle away for hours warming up before you ride it, in fact I suspect that may be part of the reason plugs die prematurely.
Of course I don't give it a hiding from dead-cold, and I ride it conservatively whilst it comes up to temperature like I do with all my other bikes. I'm mindful that a Wankel heats and cools differently than a 'normal' engine. I've not had any issues so far.
I suspect the advice from Suzuki (and Sam as well?) about a lengthy warm-up is a bit of an arse-covering exercise.
They were obviously concerned with longevity/rotor sealing issues and persuading owners to be careful is prudent, especially given some of the lunk-heads out there.
I'll keep you up to date with any changes and/or revelations. If you have an opportunity, please give me a call and I can discuss further stuff with you.
I'll be on the RE for next year's Bathurst Rally and I'm looking forward to forming (re-forming?) the RE club down there.
And, feel free to pass my deatils on - why keep this meagre Suzuki knowledge to myself?
Cheers
Paul
* There is BTW a way to determine the port-valve to secondary butterfly synchronisation without using the protractor. You can see when the secondary butterfly is about to open by observing the movement of the limiting-plate - you can see it through the frame from the RHS. Then it's a simple matter of getting someone (like your long-suffering partner) to observe how far, or not, the port valve has opened/moved at that throttle opening.
A bit of back-and forth and you've got it sussed.
