I am now on my 2nd 2019 Street Glide. The first, a 'Standard' with a 107 engine, was repurchased by HD due to an engine noise that was seemingly non-repairable. Dealer had the bike for over 40 days and HD couldn't tell the dealer 'what' or 'how' to fix the noise problem, so I simply enacted our State's Lemon Law and had HD replace the bike. In so doing, I moved from the Standard to the 'Special', which has the 114 M8 motor. Both bikes have remained 100% 'stock', as I purchased them for long-distance trips, and really have no need for additional power.......or 'noise'. So, in riding the first bike through the first 1000 miles, I noted a noise that I considered to be 'detonation'. I informed my selling dealer of the issue, and was told to continue to ride the bike to see if it went away. I then took a 2500 mile run on the bike and during this trip the noise continued. Upon my return, I took it back to my selling dealer where upon they claimed 'not' to hear anything. As this was a totally unsatisfactory answer, I took it to another more 'service reputable' dealer. They instantly heard the noise, but were unsure of 'exactly' just what it was. Long story short, they made some audio recordings of the noise while in the quiet of a 'dyno-room', and sent these recordings to the Motor Company for further review. Unfortunately, HD never did get back to them with an answer.......and after nearly a month and a half, I decided I simply didn't trust the bike........and requested HD replace it under the Lemon Law. They did! I now own the new bike. And.......while not nearly as severe as the last one, it too makes the same 'noise'. Let me try to describe it as best possible:
When riding at virtually any steady speed, the noise isn't there. ONLY when 'accelerating' does the noise present itself. Generally I will cruise the bike at about 2500 rpm in what ever gear suits the speed and terrain being traveled. I do NOT 'lug' my engines....EVER!! So, take that"you're not down shifting soon enough!" response OUT of this scenario. And, the noise itself is NOT present until crossing the 2500 rpm range. It enters as a sort of 'cackle' sound that begins at about 2600 to 2700 rpm, and essentially remains present up to about 3500, and then diminishes and is gone by about 4K. It is directly related to throttle pressure and 'load' as presented by the terrain and conditions. If you SLOWLY twist the throttle on flat or down hill road you can basically ride through the noise while accelerating. However, if you twist the throttle and expect to accelerate quickly, OR......if you're working your way up a steep incline.....the noise will be present. The 'level' of the noise is somewhat dependent on this load and throttle position. More load, more throttle.....more noise present.
In my experience, this type of condition is generally characterized by what in 'engineering terms' is referred to as 'pre detonation', or more commonly referred to as 'spark knock'. I would note that the M8 motor has 'detonation sensors' installed as part of the engine control system...... so clearly the issue was one that HD took seriously enough that the incorporated these sensors into both design and production. I'm quite sure they will claim that 'detonation' is NOT a problem with the M8 motor because of this. However, my experience is rather contrary in that regard. I will admit that this noise is not the same as what I've heard on other 'non-M8' motors when they clearly WERE pre detonating. I've had twin-cam motors that 'spark-knocked' like the devil......and further tuning resolved the issue. However, this M8 motor is running in bone-stock condition......and should (by all 'factory' claims) NOT have any spark knock problems under most any circumstances. For the record, I run ONLY either Shell premium grade fuel, or Sunoco Super Premium. I don't believe 'poor fuel quality' is a contributor to this, as I purchased fuel in 4 different States, and the problem remain consistent throughout the whole trip.
Anyway, my new 114 motor is showing signs of having the same condition....though not as clearly obvious and not as severe as the prior 107. Because the M8 is a substantially different motor than HD has produced in the past, I'm willing to be open to some other explanation for this problem OTHER than being pre detonation, or 'spark knock'. BUT....... I can't find anyone who has enough true technical knowledge to be able to even discuss the issue as related to the 4-valve motor and what effect that might have. Because the 4-valve head disperses air/fuel mixture differently, there are other possibilities that may exist. This motor DOES run at a higher compression ratio than past 'stock' HD motors..... and HD had to also install compression release mechanisms in order to get satisfactory 'starting' performance from the engine. It's a 'closed loop' EFI system......and with the included detonation sensors, you'd think that if running too lean or having a timing curve that was too far advanced was the problem, the motorcycle's ECU would be capable of self-correction. BUT...... if the oddness of this noise is a function of that 'self-correction' running right on the ragged edge of being 'un-corrected'....then maybe that's it!! My gut tells me.... IT IS! I just can't get a confirmation one way or another. And, like I mentioned, the Motor Company failed to respond to the dealer about the situation......and the lead tech there is simply bewildered.
Let me conclude this saga by saying that I know no one will be able to diagnose this thing via forum posts. And, if mine's doing it, then if others are doing it too, why is there not a litany of other complaints out there? My response to that is simply that 'most' guys would probably have already put slip-on exhausts and 'tuners' on the bike by now, as well as high-flow air intakes and perhaps other 'performance' stuff........so they're probably NOT 'listening' to the engine the way I do. But, I'd almost bet the farm that in 'stock' form, their bikes did it too. In any event, I'm now 2 for 2....and just looking for an answer. Any help or suggestions would be appreciated. I'll just end by saying that adding a tuner is a possibility AFTER the 2-year warranty expires. The new HD policy of voiding one's warranty if any evidence of an after-market tuner is installed is present is problem I don't want to get in to. So, bike is staying 'stock' for the time being.
Thanks the time in reading through all this!! Tom D.
When riding at virtually any steady speed, the noise isn't there. ONLY when 'accelerating' does the noise present itself. Generally I will cruise the bike at about 2500 rpm in what ever gear suits the speed and terrain being traveled. I do NOT 'lug' my engines....EVER!! So, take that"you're not down shifting soon enough!" response OUT of this scenario. And, the noise itself is NOT present until crossing the 2500 rpm range. It enters as a sort of 'cackle' sound that begins at about 2600 to 2700 rpm, and essentially remains present up to about 3500, and then diminishes and is gone by about 4K. It is directly related to throttle pressure and 'load' as presented by the terrain and conditions. If you SLOWLY twist the throttle on flat or down hill road you can basically ride through the noise while accelerating. However, if you twist the throttle and expect to accelerate quickly, OR......if you're working your way up a steep incline.....the noise will be present. The 'level' of the noise is somewhat dependent on this load and throttle position. More load, more throttle.....more noise present.
In my experience, this type of condition is generally characterized by what in 'engineering terms' is referred to as 'pre detonation', or more commonly referred to as 'spark knock'. I would note that the M8 motor has 'detonation sensors' installed as part of the engine control system...... so clearly the issue was one that HD took seriously enough that the incorporated these sensors into both design and production. I'm quite sure they will claim that 'detonation' is NOT a problem with the M8 motor because of this. However, my experience is rather contrary in that regard. I will admit that this noise is not the same as what I've heard on other 'non-M8' motors when they clearly WERE pre detonating. I've had twin-cam motors that 'spark-knocked' like the devil......and further tuning resolved the issue. However, this M8 motor is running in bone-stock condition......and should (by all 'factory' claims) NOT have any spark knock problems under most any circumstances. For the record, I run ONLY either Shell premium grade fuel, or Sunoco Super Premium. I don't believe 'poor fuel quality' is a contributor to this, as I purchased fuel in 4 different States, and the problem remain consistent throughout the whole trip.
Anyway, my new 114 motor is showing signs of having the same condition....though not as clearly obvious and not as severe as the prior 107. Because the M8 is a substantially different motor than HD has produced in the past, I'm willing to be open to some other explanation for this problem OTHER than being pre detonation, or 'spark knock'. BUT....... I can't find anyone who has enough true technical knowledge to be able to even discuss the issue as related to the 4-valve motor and what effect that might have. Because the 4-valve head disperses air/fuel mixture differently, there are other possibilities that may exist. This motor DOES run at a higher compression ratio than past 'stock' HD motors..... and HD had to also install compression release mechanisms in order to get satisfactory 'starting' performance from the engine. It's a 'closed loop' EFI system......and with the included detonation sensors, you'd think that if running too lean or having a timing curve that was too far advanced was the problem, the motorcycle's ECU would be capable of self-correction. BUT...... if the oddness of this noise is a function of that 'self-correction' running right on the ragged edge of being 'un-corrected'....then maybe that's it!! My gut tells me.... IT IS! I just can't get a confirmation one way or another. And, like I mentioned, the Motor Company failed to respond to the dealer about the situation......and the lead tech there is simply bewildered.
Let me conclude this saga by saying that I know no one will be able to diagnose this thing via forum posts. And, if mine's doing it, then if others are doing it too, why is there not a litany of other complaints out there? My response to that is simply that 'most' guys would probably have already put slip-on exhausts and 'tuners' on the bike by now, as well as high-flow air intakes and perhaps other 'performance' stuff........so they're probably NOT 'listening' to the engine the way I do. But, I'd almost bet the farm that in 'stock' form, their bikes did it too. In any event, I'm now 2 for 2....and just looking for an answer. Any help or suggestions would be appreciated. I'll just end by saying that adding a tuner is a possibility AFTER the 2-year warranty expires. The new HD policy of voiding one's warranty if any evidence of an after-market tuner is installed is present is problem I don't want to get in to. So, bike is staying 'stock' for the time being.
Thanks the time in reading through all this!! Tom D.