Low mpg and slight power degradation

[Cosmin]

Hello everyone,

After reading many similar topics related to low mpg, I'm writing here hoping to find out a solution for my problem.

Short story: in the past 10-15.000miles I noticed a mpg degradation and I'm quite sure it is associated with a slight engine power decrease.

Now some more details regarding the symptoms etc:

- fuel consumption decreased lately; the first alarm signal was last year when the motorbike vacation involved a long highway trip across Europe till the destination (Ireland). Although I kept the usual highway riding conditions (heavy paniers + topcase + tankbag, pillion, steady 100mph with 115mph spikes) the tank range decreased to around 140miles from previous 175-185 miles;

- this year I went again on a similar trip and the same issue was noticed on the highway at steady 100mph;

- similar results were identified also at measuring consumption with tank full-to-full method: I found my old thread on a local forum in the FJR section and I was reporting at that time (bike had 10.000miles) some 31-34mpg for riding at 100-110. Now the mpg decreased to 26-28mpg in similar speed and load conditions;

Additionally to the mpg issue I am pretty sure the bike has a slight power decrease (which logically causes the mpg issue). Initially while day by day riding I thought it's only my obsession, I am too used to the bike and that's why I have the impression the power is less. But later I noticed also that:

- while riding on the same mountain twisties we did in the past 5 years with my 2 buddies (both with BMW lower powered bikes) lately I realised that I need to shift down in second more frequent. Initially I thought they improved their skills but now I think that third gear is not delivering the same power needed on that roads anymore (for the same riding style)

- I also use a throttle cramp buster from Scottoiler; I always keep it more or less in the same angle on the throttle grip in order not to be too high in "idle position" and to assure a confortable hand/wrist position at steady highway riding. I noticed that at steady 100 riding the angle of the throttle seems to be wider than it used to be; I know such measurement cannot count as precise but I'm sure the difference exist;

- also lately (I mean latest 10-15.000miles) while descending on mountain roads (overrun) especially in second gear at higher RPM (above 6500-7000) I can hear very light backfires in the exhaust (I suppose they are there also in higher gears at high rpm but the speed is bigger and I cannot hear them). The backfires are not many or very loud by they are there and I am pretty sure they were not there 20 or 30.000miles ago...

Needless to say that all the basic mpg increase factors have been checked (proper tyres pressure, no brakes lock identified, air filter renewed every 10.000miles, spark plugs renewed every 12.000miles, no gas smell or leaks etc). Recently I did also a TBS but I'm not very satisfied with the result (at least at idle), so I'll repeat it after I purchase the new twinmax balancer (I used needle type vacuums which are BS ).

The bike has now 54.000 miles and was checked for valve adjustment at 33.000; the mechanic told me (I didn't have time to assist him) that he didn't identify needs for adjustments. He also performed a TB cleaning (with throttle bodies removed from the bike) and TBS at that time. Also I suppose that if he didn't adjust the valves he also did not remove the chain/sprokets, so out of timing issue following his check should be out of discussion, right?

Still (after reading several topics) the only hint I have would be related to a timing issue (one tooth jump perhaps?!) but I understood in such a case the power delivery difference would be much more visible. Also related to common CCT issues - I haven't identified the specific noise yet...

Unfortunately I keep the bike in a garage at my parents in a mountain area (almost 2 hours drive from my place). I go there every weekend and the weekend is the only timeslot available for working on the bike (along with spending time with family, going for a ride etc), That's why I prefer to "outsource" time consuming tasks like valve adjusting to the mechanic (even if I could do it much more careful, paying attention to each detail etc than him). Though if everyone bets on timing/CCT issues I'll need to bring the bike again in my city to the mechanic and ask him for a valve check/adjustment. This time I'll ask him to call me when he finishes all the dismantling etc and I'll check with my own eyes the proper signs alignment etc (thanks to the valuable info found on the forum - RadioHowie, HaulinAshe etc).

Any advice or suggestions on possible causes is welcome.

Thanks.

 

[C&C]

I think you may have identified the problem, since I'm assuming this degradation started after the valve check (valve chain skipped a tooth). If this is not the case I think my next check would be a compression test. Others with significantly more knowledge are sure to chime in; good luck.

 

[r1byker]

I've not heard anyone else on the forum have this problem, but I had similar symptoms and it turned out to be carbon build-up on the valves. That was at about 44,000 miles. They had to dismantle the top end to fix the problem. I ended up with quite a few new top end parts. Good luck.

 

[Constant Mesh]

New windshield? At triple digit speeds a small change in aerodynamics would have a profound effect on the power required.

When he removed the TBs for cleaning he may have introduced a problem.

 

[JamesK]

With the cams and chain NOT having been removed is even possible for the chain to jump a tooth? If it was that easy wouldn't more FJR engines do that and as we know two jumped teeth on the chain means engine detonation...

 

[Cosmin]

I've not heard anyone else on the forum have this problem, but I had similar symptoms and it turned out to be carbon build-up on the valves. That was at about 44,000 miles. They had to dismantle the top end to fix the problem. I ended up with quite a few new top end parts. Good luck.

On the other hand I've never heard of this issue (carbon build-up on valves) on the FJR; is it a model specific issue? Did the mechanic mention a possible reason for this? It might explain also the light backfires I can hear at high rpm in overrun...

New windshield? At triple digit speeds a small change in aerodynamics would have a profound effect on the power required.
When he removed the TBs for cleaning he may have introduced a problem.

I also thought about the windshield - it was the case this year since I used the taller touring one; though last year I used the one (small OEM + Laminar Lip) which I've been using since I bought the bike, so I doubt this is the reason. Still I mentioned that I feel like the bike lost a bit of power also at low speeds, when the windshield doesn't matter that much.

What do you mean by problem introduced after TBs removed and cleaned? Not mounted back correctly? I might think only about not tightly screwed collars which might allow some air to go in, bypassing the air filter but I don't know if that can cause such symptoms (if it was a carbureted bike things would have been different in such a situation).

I think you may have identified the problem, since I'm assuming this degradation started after the valve check (valve chain skipped a tooth). If this is not the case I think my next check would be a compression test. Others with significantly more knowledge are sure to chime in; good luck.

I think at the valve check he only rotated the engine with caps removed, I don't think he touched the CCT, chain or sprokets, so there should be no reason to skip one tooth at that check. I'm just trying to remember the precise chronology but I'm quite sure the power degradation started a little before the valve check, so a mistake made by the mechanic (causing one tooth skip) starts to be deleted from the list...

With the cams and chain NOT having been removed is even possible for the chain to jump a tooth? If it was that easy wouldn't more FJR engines do that and as we know two jumped teeth on the chain means engine detonation...

I doubt that only inspecting the valve clearance (with CCT, sprokets and chain in place) could cause one tooth jump - I hope the more experienced guys can give some input here. Anyway, as I mentioned above, I'm almost sure the slight power degradation started a little before the valve inspection.

Thanks everyone for the replies.

 

[Donal]

What sort of fuel are you using? The best (usually the most expensive) fuels will help to keep your engine clean and in good running order. Not sure what the availability is in Romania...........

If you suspect that the fuel you can get is not up to doing the job then you will need to consider using an additive. Is "Sea Foam" available to you?

 

[Cosmin]

What sort of fuel are you using? The best (usually the most expensive) fuels will help to keep your engine clean and in good running order. Not sure what the availability is in Romania...........
If you suspect that the fuel you can get is not up to doing the job then you will need to consider using an additive. Is "Sea Foam" available to you?

While riding in Romania I'm using mainly fuel from a provider who uses cleaning aditives and has a good local reputation (also in some tests they obtained good results for gasoline quality). Anyway most of the miles on my bike ar made abroad during the vacation and I use the gas I find in good brand gas stations accross Europe (OMV, BP, Aral, Shell etc).

I also used twice some cleaning additives but I didn't notice any improvement. I'll have a check for Sea Foam availability also...

 

[Donal]

The other alternative is 'Yamaha Ring Free', fishermen swear by it for use in outboard engines. They recommend using it as follows - Perform an initial shock rate at 2oz per gallon of fuel. Then use Ring Free after that shocker at 1oz per 10 gallons of fuel.

Both of these additives are available in the UK either on Amazon or E-bay. Just a matter of hunting around for the best price. I guess P&P could be an issue for you.

If you need any help I can get it and forward on (assuming there are no issues with posting the stuff).

 

[RichDoyle]

This somewhat off the wall, perhaps, but it is something I've seen on both my ST1300s: A malfunctioning thermostat. Specifically stuck open or opening too soon. A drop in gas mileage was definitely one of the symptoms. Basically the bike didn't get fully warmed up and this presumably caused the FI system to run it richer than optimal. On the first bike the temperature routinely ran one "bar" lower than it normally did. On the second the temperature effect was even more obvious. The temperature would run one bar lower than normal generally, would sometimes get up to normal, and then drop as far as 2 bars below normal at highway speed. In both cases changing the thermostat eliminated the problem.

Running at high speeds might mask this behavior, but it might also make it irrelevant. But something to consider.

 

[RadioHowie]

Good point, Rich....sometimes "we" tend to over-think things and forget things as simple as a thermostat stuck open.

 

[Cosmin]

The other alternative is 'Yamaha Ring Free', fishermen swear by it for use in outboard engines. They recommend using it as follows - Perform an initial shock rate at 2oz per gallon of fuel. Then use Ring Free after that shocker at 1oz per 10 gallons of fuel.
Both of these additives are available in the UK either on Amazon or E-bay. Just a matter of hunting around for the best price. I guess P&P could be an issue for you.

If you need any help I can get it and forward on (assuming there are no issues with posting the stuff).

Thanks for recommendation and offer to help. I'll have a check locally and see if I can get it or else I'll let you know and arrange the order/postage.

This somewhat off the wall, perhaps, but it is something I've seen on both my ST1300s: A malfunctioning thermostat. Specifically stuck open or opening too soon. A drop in gas mileage was definitely one of the symptoms. Basically the bike didn't get fully warmed up and this presumably caused the FI system to run it richer than optimal. On the first bike the temperature routinely ran one "bar" lower than it normally did. On the second the temperature effect was even more obvious. The temperature would run one bar lower than normal generally, would sometimes get up to normal, and then drop as far as 2 bars below normal at highway speed. In both cases changing the thermostat eliminated the problem.
Running at high speeds might mask this behavior, but it might also make it irrelevant. But something to consider.

Thanks for suggestion. I think that the thermostat is ok since I usually pay attention while riding at the temp gauge and I can say it displays the same 4 bars during normal riding (gradually increasing if riding at very slow speeds or standing) and the heating time of the engine after cold start is still very short. I'll have a check anyway with an additional thermometer for the approximate opening temp of the thermostat and for the real "normal" operating temp of the engine.

 

[supertankerm60a3]

If we are using suggestions, I second the windshield issue. I just put on my fall/spring shield (+4 over my 03) and I do not have numbers HOWEVER, I used to go two trips up and back for exactly $20 with one quart of extra gas in the little can i would take to the station. after 3 fill ups I would have 3 quarts extra. last week I changed shields now I am at just a little deficit on the $/distance ratios.

Considering that aerodynamic resistance goes up at the cube of your speed, and you had quite a bit of speed, the shield could account for the drop in mileage.

 

[user 8909]

I got my worst milage ever going to Maggie which was mostly slab, but I was running around 80mph with the windshield all the way up and loaded panniers. 35mpg.

And I think my front tire may have helped in those low numbers too.

 

[Cosmin]

If we are using suggestions, I second the windshield issue. I just put on my fall/spring shield (+4 over my 03) and I do not have numbers HOWEVER, I used to go two trips up and back for exactly $20 with one quart of extra gas in the little can i would take to the station. after 3 fill ups I would have 3 quarts extra. last week I changed shields now I am at just a little deficit on the $/distance ratios.
Considering that aerodynamic resistance goes up at the cube of your speed, and you had quite a bit of speed, the shield could account for the drop in mileage.

I got my worst milage ever going to Maggie which was mostly slab, but I was running around 80mph with the windshield all the way up and loaded panniers. 35mpg.

And I think my front tire may have helped in those low numbers too.

This was also a hint to me but it applies only for the long trip performed this year when I used the tall touring whindshield. But the problem occured also last summer when I was using the same small OEM windshield plus LaminarLip I've been using since the bike was new, so the this cannot be the reason...

 

[Donal]

Oops, it's apology time. When I looked yesterday (just a quick glance) I could see that 'Yamaha Ring Free' WAS available on e-bay & Amazon. However, when I looked in more detail, all the suppliers are based in the USA!......... The P&P rates are prohibitive.

I haves searched the UK and it just doesn't appear to be stocked anywhere. I have no idea why.

If you can locate some in the UK I am still happy to buy it and forward on to you if that is any help.

Once again, I am sorry for making an offer I couldn't fulfil............

 

[Cosmin]

Oops, it's apology time. When I looked yesterday (just a quick glance) I could see that 'Yamaha Ring Free' WAS available on e-bay & Amazon. However, when I looked in more detail, all the suppliers are based in the USA!......... The P&P rates are prohibitive.
I haves searched the UK and it just doesn't appear to be stocked anywhere. I have no idea why.

If you can locate some in the UK I am still happy to buy it and forward on to you if that is any help.

Once again, I am sorry for making an offer I couldn't fulfil............

No worry, thanks for the offer and help.

At a quick search I found the next offers for SeaFoam and Yamaha Ring Free (though Ring Free is much more expansive?!):

https://www.amazon.com/Sea-Foam-SF-16-Motor-Treatment/dp/B0002JN2EU#productDetails

https://www.amazon.com/Yamaha-Ring-Additive-32oz-ACC-RNGFR-32-00/dp/B002GUCLH2

So, if you cofirm these are the products in discussion, I will try to arrange with a local dealer who can arrange orders from USA and go for the SeaFoam. I have two buddies interested also, so we can order a higher quantity and split transport and other fees.

Thanks.

 

[C&C]

Seafoam is light oil (similar to diesel fuel), alcohol (isopropanol, I believe) and naphtha (probably the carbon dissolving portion of the mix); it might help. I don't know what Ring free is made of though and either could be a first step to try.

 

[Cosmin]

Seafoam is light oil (similar to diesel fuel), alcohol (isopropanol, I believe) and naphtha (probably the carbon dissolving portion of the mix); it might help. I don't know what Ring free is made of though and either could be a first step to try.

Thanks for details; can you confirm - the one belowis the one used by everybody?

https://www.amazon.com/Sea-Foam-SF-16-Motor-Treatment/dp/B0002JN2EU#productDetails

Together with another 2 bikers we'll place an order for several bottles and we want to make sure we order the right product.