Torque dip .. suggestions?
HDF Community Team
Joined: Jun 2006
Posts: 12,763
Likes: 2,597
From: san antonio
i respect Dave's knowledge but was thinking of several issues that could cause the TQ dip.
Tune; could be the tune, pretty basic and the AFR line would help.
Exhaust; even though the Boarzilla was recommended, i would try another exhaust, even the OEM system and do a couple of pulls to see if the dip goes away. The numbers might drop but if the curve looks good; problem solved. If the issue remains, it's not the Boarzilla.
Clutch; check adjustment? A motor making that much power should have a VPC or something similar with a strong spring. The OP should consider adding a Tiamchi (AIM) clutch hat with the correct spring, Barnett Scorpion or something similar anyway.
Sumping; does tghe moto get hot when this is going on? If the motor is sumping badly, it is like dragging an anchor; however, aside from making the motor run hot, sumping will also hold TQ/HP down but the motor doesn't appear to have any problem making power.
As usual, JMHO.
Tune; could be the tune, pretty basic and the AFR line would help.
Exhaust; even though the Boarzilla was recommended, i would try another exhaust, even the OEM system and do a couple of pulls to see if the dip goes away. The numbers might drop but if the curve looks good; problem solved. If the issue remains, it's not the Boarzilla.
Clutch; check adjustment? A motor making that much power should have a VPC or something similar with a strong spring. The OP should consider adding a Tiamchi (AIM) clutch hat with the correct spring, Barnett Scorpion or something similar anyway.
Sumping; does tghe moto get hot when this is going on? If the motor is sumping badly, it is like dragging an anchor; however, aside from making the motor run hot, sumping will also hold TQ/HP down but the motor doesn't appear to have any problem making power.
As usual, JMHO.
Last edited by djl; Mar 30, 2020 at 11:05 PM.
Road Warrior
Joined: May 2011
Posts: 1,956
Likes: 437
From: florida
Good advice by all. Sucks to troubleshoot but on a nice build you have to find the problem. Smart guys on here, even if it’s not clutch and it could be, you should beef up anyhow. Like advised a lock up hat and spring or cheapest attempt would be heavy spring as suggested. I have an extra AIM 480 spring sitting here w almost no miles on it if you’re interested in trying that first.
Sponsor
Joined: Dec 2007
Posts: 12,084
Likes: 829
Where the engine is doing the most work, it requires the most fuel.
Could be that simple, unless it is being drowned.
If clutch slippage was that pronounced, then it should have been evident to the dyno folks, and a quick phone call to alert/correct.
Scott
Could be that simple, unless it is being drowned.
If clutch slippage was that pronounced, then it should have been evident to the dyno folks, and a quick phone call to alert/correct.
Scott
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Intermediate
Joined: Jan 2020
Posts: 47
Likes: 0
From: Indiana
Thread Starter
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Intermediate
Joined: Jan 2020
Posts: 47
Likes: 0
From: Indiana
Afr and timing
Grand HDF Member
Joined: May 2014
Posts: 3,814
Likes: 1,168
From: florida
You need to take the bike to another shop with some better equipment, unless your tuner can convert your 02 sensor voltages into some kind of plotted graph. The timing for that build is also not where it should be, especially if you comp is 10.5 or more. My bet is still on clutch slip. The Scorpian clutch is very cool, just picked one up myself.
m
m
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Intermediate
Joined: Jan 2020
Posts: 47
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From: Indiana
You need to take the bike to another shop with some better equipment, unless your tuner can convert your 02 sensor voltages into some kind of plotted graph. The timing for that build is also not where it should be, especially if you comp is 10.5 or more. My bet is still on clutch slip. The Scorpian clutch is very cool, just picked one up myself.
m
m
Grand HDF Member
Joined: May 2014
Posts: 3,814
Likes: 1,168
From: florida
Diagnose the issue first before you spend big money on high dollar unit like a scorpion or a pro clutch. The SE spring is cheap and if it cures the issue, then you can decide if you want to upgrade to the more expensive stuff. The idea is to KNOW that that is the issue, before spending. I dont particularly care for hydraulic on HD, but thats just me. The reason I wanted the scorpion was because it uses coil springs instead of a diaphragm spring, and the scorpion comes with 4 different sets of springs so that you can tune it to what you need. You can mix and match springs, the diaphragm style is not as versatile for tuning. The Pro clutch is very good, but its a diaphragm style spring.