Post by wayne on Apr 24, 2011 2:22:53 GMT -5
The Bathurst rally was fantastic with 5 rotaries in attendence.
Four were running well but one was diabolical, and I'm quoting the owner who had suffered the 1000 klm trip down.
I've ridden lots of miles with hesitations on my bike and others in the past. But they always tended to be around that 3000 rpm mark. This bike was horrible and it didn't matter what rpm you were in from 2,000 to 5,000, any attempt at a roll-on of throttle gave a kill-switch like hesitation. And any attempt at full throttle from a standing start was all but fling-you-over-the-bars hesitation.
While testing, we noticed that putting the choke on got rid of the roll on hesitation.
To cut a long story short, we looked firstly at float height and this particular carb was way out. With an L shaped card cut out to 43.3 mm float height was set. A quick visual align on the port valve (which was in the ballpark anyway) and as far as I could see, this was a different bike.
The roll-on hesitation had gone. Certainly a burble and not perfect, you could tell when it changed throats, and occasional “gulp” but the full throttle standing start was also cured.
However the owner kept telling me that it wasn't right and it was horrible. I thought we were talking about different bikes.
Two experienced motorcyclists, both A grade racers rode it and said it was not bad. However, he was the owner and rider and he was adamant and I believed him.
It took me 5 test rides along country roads before I finally got what he was saying. Sure the kill-switch hesitation was gone, but at constant rpm all of a sudden the bike would seem like it was running out of fuel. I had this for a good mile and choke did not help.
To cut another long story short, we equipped the bike with the biggest primary on hand (97.5) and a different air filter (Jess's new ones) which seemed to help a little. But it was suggested that the owner rode home on "prime".
That evening we got a text to say the bike had run better than ever before and that the petcock was indeed faulty periodically cutting fuel supply to the engine. He's been struggling with this bike for about a year.
While I believe the float height correction was the main factor in getting rid of the any-rpm hesitation, the other problem is just a typical "old bike" issue. Nothing to do with the RE5 or its carby per se but you can waste a lot of time chasing something that is simple and not just an RE problem.
Jess does emphasise elsewhere that float height is critical. The boys I ride with have gobs of racing experience and tell me that often a 1mm float height difference could significanlty affect the regular engined bikes.
There never seems to be a one hit fix..........all incremental and all from several areas.
Spoke to the owner today and he confirmed that it is now running very well and at a point where he now feels that it only needs small tweaks here and there to get it fully right.
He's also going to reduce the jet size back to something more regular. The bikes there were running either 87.5's or 90's (stock primaries), three were perfect, one was all but and only to the fussiest assesment. So you don't need excessively large primary jets but they certainly do and can help temporarily.
Personally, I’m in heaven. I’ve never had anything to teach me but my own RE5 with its own suite of problems. Riding and analysing with 4 other blokes plus a few experienced but non rotary riders was magic.
Wayne
Four were running well but one was diabolical, and I'm quoting the owner who had suffered the 1000 klm trip down.
I've ridden lots of miles with hesitations on my bike and others in the past. But they always tended to be around that 3000 rpm mark. This bike was horrible and it didn't matter what rpm you were in from 2,000 to 5,000, any attempt at a roll-on of throttle gave a kill-switch like hesitation. And any attempt at full throttle from a standing start was all but fling-you-over-the-bars hesitation.
While testing, we noticed that putting the choke on got rid of the roll on hesitation.
To cut a long story short, we looked firstly at float height and this particular carb was way out. With an L shaped card cut out to 43.3 mm float height was set. A quick visual align on the port valve (which was in the ballpark anyway) and as far as I could see, this was a different bike.
The roll-on hesitation had gone. Certainly a burble and not perfect, you could tell when it changed throats, and occasional “gulp” but the full throttle standing start was also cured.
However the owner kept telling me that it wasn't right and it was horrible. I thought we were talking about different bikes.
Two experienced motorcyclists, both A grade racers rode it and said it was not bad. However, he was the owner and rider and he was adamant and I believed him.
It took me 5 test rides along country roads before I finally got what he was saying. Sure the kill-switch hesitation was gone, but at constant rpm all of a sudden the bike would seem like it was running out of fuel. I had this for a good mile and choke did not help.
To cut another long story short, we equipped the bike with the biggest primary on hand (97.5) and a different air filter (Jess's new ones) which seemed to help a little. But it was suggested that the owner rode home on "prime".
That evening we got a text to say the bike had run better than ever before and that the petcock was indeed faulty periodically cutting fuel supply to the engine. He's been struggling with this bike for about a year.
While I believe the float height correction was the main factor in getting rid of the any-rpm hesitation, the other problem is just a typical "old bike" issue. Nothing to do with the RE5 or its carby per se but you can waste a lot of time chasing something that is simple and not just an RE problem.
Jess does emphasise elsewhere that float height is critical. The boys I ride with have gobs of racing experience and tell me that often a 1mm float height difference could significanlty affect the regular engined bikes.
There never seems to be a one hit fix..........all incremental and all from several areas.
Spoke to the owner today and he confirmed that it is now running very well and at a point where he now feels that it only needs small tweaks here and there to get it fully right.
He's also going to reduce the jet size back to something more regular. The bikes there were running either 87.5's or 90's (stock primaries), three were perfect, one was all but and only to the fussiest assesment. So you don't need excessively large primary jets but they certainly do and can help temporarily.
Personally, I’m in heaven. I’ve never had anything to teach me but my own RE5 with its own suite of problems. Riding and analysing with 4 other blokes plus a few experienced but non rotary riders was magic.
Wayne
