2018 KTM 85SX bogging

kb-450
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kb-450
Edited Date/Time 4/2/2018 12:23pm
Having an issue the bike bogging, but happens after about 2-3 laps. No bog before that and runs amazingly. Almost like a vapor lock type of bog. Continues sitting on the side of the track.

Already checked the gas cap and put a brand new plug. No change. Any other suggestions?
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23champ
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23champ 1/1/2018 2:03pm
1/1/2018 2:03pm
Check for an air leak on the intake.
HenryA
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HenryA 1/1/2018 2:09pm
1/1/2018 2:09pm
Jetted correctly? Checked if the reeds seals up?

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kb-450
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kb-450 1/1/2018 2:24pm
1/1/2018 2:24pm
Correct me if I am wrong, but I would think if it were reeds or air leak, it would show signs of the bog immediate, not after 2 to 3 laps. It runs great (perfect) for a few laps and then starts bogging. Thanks for the input, i will check both.
kb-450
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kb-450 1/1/2018 2:27pm
1/1/2018 2:27pm
Paw Paw 271 wrote:
Check you float.
Also check your carb vent lines.

Paw Paw
Carb vent lines, i do need to cut them shorter. Think a clogged vent line could cause a vapor lock type scenario?

Thx for the feedback.
Paw Paw 271
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Paw Paw 271 1/1/2018 5:27pm
1/1/2018 5:27pm
Yes, but it would be from fuel starvation, not vapor lock. If the float level is low it will also cause this issue. Also do an OHMs test on the coil.

Paw Paw
23champ
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23champ 1/1/2018 5:47pm
1/1/2018 5:47pm
kb-450 wrote:
Correct me if I am wrong, but I would think if it were reeds or air leak, it would show signs of the bog immediate, not...
Correct me if I am wrong, but I would think if it were reeds or air leak, it would show signs of the bog immediate, not after 2 to 3 laps. It runs great (perfect) for a few laps and then starts bogging. Thanks for the input, i will check both.
The reed block may seal up when the engine is cold, but as the engine temp rises an air leak may form. Check the clamp on the carb also. I had the shock serviced on my ‘17 350sxf and the dealer left the airbox side clamp loose. I noticed it when I zip tied the electrical back up that they left hanging...
jcruce13
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jcruce13 4/2/2018 12:23pm
4/2/2018 12:23pm
kb-450 wrote:
Having an issue the bike bogging, but happens after about 2-3 laps. No bog before that and runs amazingly. Almost like a vapor lock type of...
Having an issue the bike bogging, but happens after about 2-3 laps. No bog before that and runs amazingly. Almost like a vapor lock type of bog. Continues sitting on the side of the track.

Already checked the gas cap and put a brand new plug. No change. Any other suggestions?
We had the same problem with our 2015 KTM 85SX... it ruined the lower end. My son kept complaining about the bike bogging down and then the lower end seized on it.... When I went up to the bike it was very hot on the lower end....

pulled the bike apart and found connecting rod bearings were toast....

I rebuilt the bike and the issue came back... bogged down on me one time and the lower end felt hot... put it back in the garage and noticed the fuel line had no fuel. Opened the fuel cap and suddenly fuel filled the line.

I pulled the line and put it into a gas can and found that it would only pour fuel for about 4 seconds before it would stop. open the gas cap and fuel started to flow again then put the gas cap back on and it stopped...

root cause was vapor lock due to the gas cap not venting...

becareful letting it continue to bog... its about 800 bucks to replace the lower end with parts only...

Just thought I would share to help someone else out. I've never seen this happen before where the root cause was the gas cap...

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