KX85 bogs when make starts at 2:nd gear

scott_nz
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scott_nz 8/21/2017 10:13am
8/21/2017 10:13am
scott_nz wrote:
we always used to go back to a 9 heat range, but most of the time used BR9EIX irdium plugs, they ran better with the hotter...
we always used to go back to a 9 heat range, but most of the time used BR9EIX irdium plugs, they ran better with the hotter plug,
Mikey77 wrote:
OK, anyway is not big money to try this plug you used. You also used bigger jets?
we were never much bigger than standard, but that will come down to different fuel blends as well,
Mikey77
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Mikey77 8/29/2017 12:52am
8/29/2017 12:52am
Tried the suggested plug NGK BR9EG , it didnt help the issue (didnt expect it either)

Today we shall try with 1 size larger jets on main and lowspeed, 142 and 40 size.

I will try get a reading from the plug after a few full throttel starts,

will try to watch my sons hand on throttle side , if he maybe after release the clutch also slightly let go of the gas and this is the reason the engine bogs, after that im all out of ideas and we need consider 1:st gears starts, I cant put more time and energy in this matter, however it gets on your head when you cant "solve" it Dizzy
yz133rider
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yz133rider 8/29/2017 1:14am
8/29/2017 1:14am
Looks too rich, but I would say add 1 tooth to the rear sprocket, tell him with starts the throttle is to be wide open and feather /finesse the clutch too keep revs up, wheelspin down etc. Even with it wide open it may bog if clutch is released too quickly,need to nail the clutch perfectly and consistently
Mikey77
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Mikey77 8/29/2017 1:36am
8/29/2017 1:36am
yz133rider wrote:
Looks too rich, but I would say add 1 tooth to the rear sprocket, tell him with starts the throttle is to be wide open and...
Looks too rich, but I would say add 1 tooth to the rear sprocket, tell him with starts the throttle is to be wide open and feather /finesse the clutch too keep revs up, wheelspin down etc. Even with it wide open it may bog if clutch is released too quickly,need to nail the clutch perfectly and consistently
Can be to rich but temperature is dropping, (about 5-10 degrees) and little more oxygen in the air, so it might work, I will test anyway , its quick work to change back.

for sure my son is not enough friends with the cluch and that clutch control is definetly something we must work on, he is small in his build and small hands so both riding with 2 finger on clutch and on break lever is hard, he feels he loose the control of the handlebar.

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FIREfish148
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FIREfish148 8/29/2017 2:16am
8/29/2017 2:16am
Not enough RPM's have him ride a 250f and I bet he will want to find more power on his 85, hence learn how to use the clutch.
Mikey77
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Mikey77 8/29/2017 2:26am
8/29/2017 2:26am
FIREfish148 wrote:
Not enough RPM's have him ride a 250f and I bet he will want to find more power on his 85, hence learn how to use...
Not enough RPM's have him ride a 250f and I bet he will want to find more power on his 85, hence learn how to use the clutch.
He he, yeah that would be a sight watch that 250f ride around his 70 pounds onboard Grinning
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kzizok 8/29/2017 5:05pm
8/29/2017 5:05pm
Are you able to get it on video and post it here? If so, that may help get closer to a diagnosis with more eyes on it.
bd
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bd 8/29/2017 11:49pm
8/29/2017 11:49pm
Starts in second gear on a 80cc?
Mikey77
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Mikey77 8/30/2017 12:07am
8/30/2017 12:07am
kzizok wrote:
Are you able to get it on video and post it here? If so, that may help get closer to a diagnosis with more eyes on...
Are you able to get it on video and post it here? If so, that may help get closer to a diagnosis with more eyes on it.
Hi,

actually the new jetting and new plug worked well yesterday, I have recorded video on my phone

we discovered one rider error, my son realy rev the bike before let go of the clutch, but sometimes after the start he try stand up to quickly to be able to shift gear (he have little problem shift from sitting down) and when he does it he slightly let go of the gas and the revs get lower and when he get back on the gas it bogs just because at that point the power/speed/traction/revs combo just isnt good. A modified engine might have been able to pull thru but not this stock one.

How ever most start attempts yesterday worked out well, I told him to sit longer and use 2:nd gear for a few meters more before shift up to 3:d

can video be embed from harddrive or must upload to some site first?
Mikey77
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Mikey77 8/30/2017 12:09am
8/30/2017 12:09am
bd wrote:
Starts in second gear on a 80cc?
Yes, I think most do, atleast around our place.
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Mikey77 8/30/2017 12:33am
8/30/2017 12:33am Edited Date/Time 8/30/2017 3:46am
kzizok wrote:
Are you able to get it on video and post it here? If so, that may help get closer to a diagnosis with more eyes on...
Are you able to get it on video and post it here? If so, that may help get closer to a diagnosis with more eyes on it.
this is link to my Instagram where video is uploaded: https://www.instagram.com/mikaelhylander77/
Tom711
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Tom711 1/1/2018 8:09am
1/1/2018 8:09am
Mikey77 wrote:
Hi, My sons kx85 -17, sometimes bogs when he shall make a start at 2:nd gear. It was worse with the Pro Circuit pipe/silencer so I...
Hi,

My sons kx85 -17, sometimes bogs when he shall make a start at 2:nd gear. It was worse with the Pro Circuit pipe/silencer so I changed back to the HGS exhaust-system and thought I "solved" it because the bike didnt bog anymore when he did the start training.

But now the problem seem to come back.

I run the stock jetting. According to the manual for our current weather (temp + altitude) Stock should be the right setting. And the bike runs very well on the track, it also answers well when twist the throttle with no gear.

I did tried bigger jets but it didnt solve the issue of boging.

I have cleaned the exhaust valve so I dont think that would be the issue either. (bike has about 30h and the piston about 10) It did bog also right after the piston was changed

Sometimes he can make 3-4 starts on 2:nd and it works fine and then for the next starts it bogs right after he let go of the clutch. Maybe the increased engine temperature makes it bog?

When start at 1:st gear there is no issue.

Any ideas?

//Mikael
Apologies for dragging up and hijacking a old thread but I’m just interested in how you found the hgs and pro Circuit pipes? We’re in the uk so our tracks vary massively from tight twisty hard pack in summer to deep sand (and mud) in winter so looking for something that gives broad power throughout.
Mikey77
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Mikey77 4/3/2018 12:40pm
4/3/2018 12:40pm
Tom711 wrote:
Apologies for dragging up and hijacking a old thread but I’m just interested in how you found the hgs and pro Circuit pipes? We’re in the...
Apologies for dragging up and hijacking a old thread but I’m just interested in how you found the hgs and pro Circuit pipes? We’re in the uk so our tracks vary massively from tight twisty hard pack in summer to deep sand (and mud) in winter so looking for something that gives broad power throughout.
Hi. Sorry for late answer.

PC is for sure more power to the top. Suiteble for tracks with long straights and wide corners

The HGS is more smooth and works more on bottom and mid, suiteble for more tricky tracks with tight corners where engine needs to start working from the bottom alot.

My son favors the HGS mostly.

We did buy the V-force 3 intake and a VHM top. I also mod the carb myself (increased the diameter maybe 1mm) and applied the suiteble jetting to match the other mods. 42 in pilot and 148 in main at the moment.
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FlickitFlat 4/3/2018 1:11pm
4/3/2018 1:11pm
I was going to suggest reeds since no one mentioned it. But you said you got a V-force intake. Did the problem start then? If that was the case I would say Jetting for sure. But my first inclination before reading was a defective reed or power valves incorrect. jetting would be my 3rd suggestion, but after reading, I'd lean toward that direction.
I had RM 80's and KX 80's and both would flip the bike 5 foot in the air in 2nd gear with stock gearing if you wanted. I had a dumb ass friend that proved it once for me... by accident. I've pulled 3rd gear starts on wet days with both RM and KX bikes as well. I'm just saying, they were all fire breathers. The only bog issues I ever had was trying to time my gearing between jumps with being 6 speeds. Never off the line. God I miss riding 80's.
Mikey77
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Mikey77 4/3/2018 1:24pm
4/3/2018 1:24pm
FlickitFlat wrote:
I was going to suggest reeds since no one mentioned it. But you said you got a V-force intake. Did the problem start then? If that...
I was going to suggest reeds since no one mentioned it. But you said you got a V-force intake. Did the problem start then? If that was the case I would say Jetting for sure. But my first inclination before reading was a defective reed or power valves incorrect. jetting would be my 3rd suggestion, but after reading, I'd lean toward that direction.
I had RM 80's and KX 80's and both would flip the bike 5 foot in the air in 2nd gear with stock gearing if you wanted. I had a dumb ass friend that proved it once for me... by accident. I've pulled 3rd gear starts on wet days with both RM and KX bikes as well. I'm just saying, they were all fire breathers. The only bog issues I ever had was trying to time my gearing between jumps with being 6 speeds. Never off the line. God I miss riding 80's.
Well i think we solved it, i guess it came down to both the bike but also my sons starting technic. starts and then came the booging. I meen bike did not change and my son pretty much did the starts the same. I can only imagine the increase of heat to the engine partialy caused the booging.

To the racebike we did also have the cylinder ported and the case port-matched to the cylinder. Boysen waterpump and Liquide Ice coolant.

I hope these issuse is not coming back, ever...HuhTongue



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