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Post by hudson on Mar 19, 2020 10:32:45 GMT -5
I also would like to Thank pmcburney for his reality check on carburetor swaps. I didn't want to comment that a random carburetor swap wouldn't be anywhere near a correct working stock carburetor without more work that can be described on here. Getting a Carb.swap to have good to near perfect drive ability is a monumental task I have undertaken a few times with good results and more hours than I could count, and proves how good the manufactures are at achieving it.
Brian
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Post by tom93gts on Mar 19, 2020 11:18:14 GMT -5
I also would like to Thank pmcburney for his reality check on carburetor swaps. I didn't want to comment that a random carburetor swap wouldn't be anywhere near a correct working stock carburetor without more work that can be described on here. Getting a Carb.swap to have good to near perfect drive ability is a monumental task I have undertaken a few times with good results and more hours than I could count, and proves how good the manufactures are at achieving it. Brian I agree and wasn't really contemplating a carb swap. I have an idea of how difficult that is because I put a Weber carb on my REPU and it took years to get that to where it was pretty much right, and that's something where all the parts are readily available, there are write ups on it, no fab work etc. I can only imagine how much effort it would be to get a carb swap working well on the RE5. I'm grateful for all the help this forum provides whenever I run in to my many carb problems. With a little luck maybe this round of carb problems will result in better fuel economy than before!
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Post by wayne on Mar 19, 2020 18:04:24 GMT -5
Today I started off by following Tim's advice and pulling down on the accelerator pump just as I get the revs up to where it stops and I got through. Then I revved up again and it went right through to 6k with no issue again, now it seems to have no issue revving, I wonder if something was just stuck on the accelerator pump and pulling down manually got it freed up? Anyway, it seems I can rev all the way through the range now. We'll see if it's still fixed tomorrow, keeping my fingers crossed on that. Next problem to work on is getting it to idle with the choke off. After warming up it stalls as soon as I switch off the choke. I think last time this happened to me it was the primary jet plugged up, but I just checked it a couple days ago. I'll pull it again but don't have much faith in that. You can disable the AP completely and other than a marked hesitation, the bike will ride and rev to 7000 rpm cleanly. I can't see it was anything to do with the accelerator pump per se that caused the inability to rev beyound 4000. The idea of using the AP as Tim described certainly helped "push" you through what seems to have been some sort of block. Well done, I hope it becomes easier from now (BTW, there's nothing wrong with correctly set up RE5 fuel consumption, ballpark the same as a GT750 M/A or B model. Not great, but "normal" for the time).
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Post by pmcburney on Mar 19, 2020 18:18:17 GMT -5
The reality is, if you've the spent time and effort trying to make a stock RE5 carb work (and likely failed as I did), you're already halfway down the path of a carb swap - you've skilled yourself up in a lot of the vagaries required to do the job already...
It's not my intention to put anyone off attempting it if (and this is a big 'if') you've got the time and those skills, because it does reap great rewards in the long run.
My bike is now completely free of any surging/hesitation and/or acceleration issues - I can crack the throttle wide-open in 1st gear from a standstill and the bike will just leap forward and run perfectly to redline. It also feels as if it has a much stronger bottom-end and the throttle is now very instant and responsive having eliminated the dreaded 'dead' feel on the primary stage of the stock carb, as there's no longer that two-stage arrangement in place. The punchy/torquey mid-range feel that these engines have has been retained or even enhanced and it will easily hold top gear up long inclines and leave almost everything else for dead in that scenario.
It does get about the same fuel economy as the stock carb (rotaries need to run rich) and it does have quite a lopey idle (I reckon it's because the pilot circuit is quite rich), but the lopey-ness disappears as soon as the throttle is opened and it doesn't affect running at all anywhere else in the rev range. It's quite a bit louder than stock as the intake of the carb is now just in front of your left knee instead of being ducted under the tank, but if you ride with hearing protection you won't hear it - it doesn't bother me at all and adds to the character of the bike IMO.
Personally I would recommend doing it, especially if absolute originality is not necessarily your thing and you're chasing a running/riding situation that the engine is capable of when carbureted properly.
Having said all that, all the modifications I made to my bike are completely and imperceptibly reversible - I would suggest NOT making mods to anything that can't be replaced or otherwise undone as RE5-specific parts are now in very short supply and becoming increasingly expensive.
For general info, as my bike hasn't been run for a while anyway, I'll take a small vid of my bike starting and running and post the link here.
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Post by wayne on Mar 19, 2020 22:28:54 GMT -5
My bike is now completely free of any surging/hesitation and/or acceleration issues - I can crack the throttle wide-open in 1st gear from a standstill and the bike will just leap forward and run perfectly to redline. Gee, so does my completely stock M model and I've already done a video! Seriously though, it is the bane of many RE5's and good luck to any alternative solutions. I worked on my A model on and off for a year and didn't completely fix the hesitation.
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Post by goandy on Mar 20, 2020 21:32:51 GMT -5
I did a SU swap on my bike. Bough an HIF38 from ebay in Wales, then had it shipped down to Australia. Much cheaper up there! The carb came off a Mini of some sort.
I cleaned the carby, put a cable pull wheel on the other side of the shaft, drilled a hole in a blank port and tapped it for the oil feed (straight into the fuel bowl) and hand drilled/die ground a chunk of alloy as the adaptor plate. Put the carby on the bike and it started first pop and has been running beautifully ever since.
Probably took me about 5-6 hours tops I guess.
I know the chap who spent hours with a wideband tuning and sanding the needle but he is particularly an@l about his bikes. Great bloke, but I really couldn't be bothered. My bike has been running the SU for 6-7 years at least with no ill effects apart from the loping idle. That idle is characteristic of the peripheral porting and Suxuki/Mikuni did very well to stifle/tune it out.
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Post by pmcburney on Mar 20, 2020 23:07:35 GMT -5
My bike has been running the SU for 6-7 years at least with no ill effects apart from the loping idle. That idle is characteristic of the peripheral porting and Suxuki/Mikuni did very well to stifle/tune it out. I reckon I can almost cure the lope on my bike (with the Mikuni carb) with a smaller pilot jet. I can almost get rid of it by screwing the pilot fuel screw all the way in, which proves that the pilot circuit is too rich (the engine doesn't die). If I can be bothered sourcing a smaller pilot jet, I'll let y'all know how it goes.
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Post by wayne on Mar 20, 2020 23:15:32 GMT -5
Indeed, the loping is part of the package. Bulletin 9 even mentions that the correct mixture at idle may cause a slight lope and it's not a problem.
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Post by goandy on Mar 21, 2020 7:03:00 GMT -5
Indeed, the loping is part of the package. Bulletin 9 even mentions that the correct mixture at idle may cause a slight lope and it's not a problem. Absolutely. It also adds heaps of character to the bike when you're sitting in traffic brapping away. Personally I love it. I forgot to mention that I didn't modify anything at all on my bike to fit the SU- the carby is carefully wrapped and kept in a box on the shelf if I ever feel the need to be original...
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Post by wayne on Mar 21, 2020 18:53:28 GMT -5
Absolutely. It also adds heaps of character to the bike when you're sitting in traffic brapping away. Personally I love it. I visited Auckland many times during my working years and it's distinctive aural feature as you strolled down Queen st was the brap brapping of highly modified RX-7's at the traffic lights. Less appealing, but still an aural signature, was the sound of unmuffled Harleys. I knew I was waking in Los Angeles.
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Post by timpa136 on Mar 22, 2020 15:21:26 GMT -5
Not sure if this is relevant or not but the earliest RE5s alternated with 2 weight rotors and the light weight rotor would lope at idle.
Tim
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Post by hudson on Mar 22, 2020 17:17:17 GMT -5
Not sure if this relevant either, But I remember doing a Proper swap under warranty that had lower compression on one side of the rotor out of the recommended parameter, and this also caused it to lope more the usual.
Brian
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Post by pmcburney on Mar 22, 2020 17:38:49 GMT -5
Just for info, it definitely is mixture related.
My bike will idle smoothly when cold and will lope when up to temp. This (to me anyway) points to a rich idle mixture being part of the 'issue'.
As I said above, If I get my hands on some smaller pilot jets I'll do an experiment to see if I can eliminate or mitigate the lope.
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Post by pmcburney on Mar 23, 2020 1:38:13 GMT -5
As promised, a short (crappy) vid of my bike with the Mikuni fitted: A couple of points to note: . No, you're not hearing things at the start of the vid - that IS a whipbird call in the background (they're common around here, I don't even notice them any more). . That's the choke I push in at about halfway through the vid - that knob is connected to a cable that runs around behind the carb to its choke plunger, . The engine is pretty-much dead cold - you'll notice how smoothly it idles at first until it warms up slightly and starts to lope, . My tach is very, very sluggish and will barely register with quick, sharp throttle openings (it's fine once you're moving as it does creep up to the correct reading eventually) - I fear the damping fluid is a little too thick...
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ap951
2nd Gear
Posts: 280
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Post by ap951 on Mar 23, 2020 6:04:06 GMT -5
really clean conversion, that's nice work there
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