Mikuni hsr 45 runs terrible at cruise speed - Yamaha Rhino Forum - Rhino Forums.net
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post #1 of 14 (permalink) Old 08-12-2011, 11:30 AM Thread Starter
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Mikuni hsr 45 runs terrible at cruise speed

Anyone know where to adjust, 686 +1 valves stage two cam

Have af guage jetting is good throughout, out of the box sudco carb bigger main, adjusted stock needle and stock pilot things just wont run at cruise speed like 1/4 throttle, is it a accelerator pump adjustment, need for a change in needle or pilot jet

As long as Im moving the throttle works good just can not cruise

sh1
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post #2 of 14 (permalink) Old 08-12-2011, 02:56 PM Thread Starter
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Anybody?

sh1
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post #3 of 14 (permalink) Old 08-12-2011, 03:34 PM
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Needle/main jet.

Try dropping your need down/or raising it up and see what happens.......

If you think it is rich lower the needle by raising the clip, or if you think it is lean raise the needle by lowering the clip...........

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post #4 of 14 (permalink) Old 08-12-2011, 05:01 PM Thread Starter
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Ifit was a 2 stroke, Id have this dialed in in a second, these rhinos with the 45 carb is a pain..ive ran the needle up and down no change..Im thinking it might be the size of needle that came with it. But Im guessing...

sh1
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post #5 of 14 (permalink) Old 08-12-2011, 09:45 PM
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What does the air fuel meter say when its running crappy at cruise?
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post #6 of 14 (permalink) Old 08-12-2011, 10:49 PM
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It may need a different tapor needle. Call Chris at benchmark........I have been down this road with a hsr48. The first part of the tapor on the need is too large causing it to run lean in thatt throttle position. The best way to get it dialed is get a wideband......

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post #7 of 14 (permalink) Old 08-12-2011, 11:56 PM Thread Starter
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Azcourt it reads fairly steady around 13

Nvs2none as far as the needle I read the tuning guide, found on this forum, and it mentio ed the size of the taper on the needle..when it sits slightly up, at part throtal, the biggining of the taper is just at the throat of the jet, but the manual says performance set ups ussually need a leaner needle..just seems backwards to me

Maybe ill call chris, I was just hopeing someone knew what setups are standard changes on a mikuni. Its fairly typical mods for a 686

The car works ok it just sucks if you want to cruise

sh1
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post #8 of 14 (permalink) Old 08-13-2011, 09:02 AM
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Strange that your AFR reads around 13.................mine would go way lean at cruising and if I raised it up to help it would be fat at WOT. So I went to a smaller tapor.....but my AFR reflected that as well...............you may have a stator/ignition issue.

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post #9 of 14 (permalink) Old 08-13-2011, 09:36 AM
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Get the leanest needle, get the leanest accelerator pump nozzle and run it around 10.5-11 on A/F at idle with the a/f screw. Running it rich at idle will help make up for it running lean in mid range. Adjust your start scfrew on the accel pump so it activates at 1/4 throttle and stop screw at adjusted at 3/4-7/8 throttle. Start from idle and work your way up to the main jet with your adjustments. This is how I ran mine and ran perfect.

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post #10 of 14 (permalink) Old 08-13-2011, 04:23 PM Thread Starter
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Thanks thats what the guide said leaner needle, but I had no idea with all the accelerator pump adjustment etc...Ill try it..Im in the middle of going through the front end for Worcs in washington..I should have time at the race to tweak it

sh1
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post #11 of 14 (permalink) Old 08-22-2011, 09:43 PM
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I had to run the leanest needle with the 660, but with 686 and 693 motors I had to go back to the stock needle. I'll see if I can find my notes on the 45 and 686 combo.
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post #12 of 14 (permalink) Old 08-23-2011, 12:08 AM
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Ifit was a 2 stroke, Id have this dialed in in a second, these rhinos with the 45 carb is a pain..ive ran the needle up and down no change..Im thinking it might be the size of needle that came with it. But Im guessing...
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post #13 of 14 (permalink) Old 08-23-2011, 09:34 AM Thread Starter
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Just got back from washington for thw Worcs race at 100-300 feet, my home is around 1200. I adjusted the fuel pump start and stop like rhinonut said and it ran the best itever had. Dont know if itwas the adjustment or the low altitude, I will run ithere at home and see if it goes to crapagain..

Court I would be interested to hear what you had

sh1
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post #14 of 14 (permalink) Old 08-23-2011, 03:32 PM
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Quote:
Originally Posted by dlytlesh1 View Post
Just got back from washington for thw Worcs race at 100-300 feet, my home is around 1200. I adjusted the fuel pump start and stop like rhinonut said and it ran the best itever had. Dont know if itwas the adjustment or the low altitude, I will run ithere at home and see if it goes to crapagain..

Court I would be interested to hear what you had
Glad it sounds like it worked. Did you get the lean accel pump nozzle as well?

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