Lost about 10 HP after valve check?

longnokr · Apr 8, 2008

I checked my valves a few weeks ago, (25k) they were all perfect so I just replaced the chain tensioner and thermostat while I was there. It all went together perfect, ran out good....just not great like before. It starts fine, runs smooth, no miss or hesitation, it just seems to have lost some grunt....and it won't power wheelie anymore!! It feels alittle flat in the midrange too. There are no fault codes, has a newer TPS, new plugs and air filter, good fuel, baro and map sensors check ok, all vac lines to pressure reg and map seem fine, all connectors are in place...is it possible the cam chain moved on the sprockets when I changed the tensioner? I didn't think there would be enough slack to jump a tooth, and I was very careful, but I'm about down to pulling the v/c back off to see if the valve timing may be off a bit...any suggestions fellow gearheads??

Geezer · Apr 8, 2008

Well, if you did not need to adjust any valves so you probably did not change the valve timing. You did check the valves with the cam chain under tension, right?

Since you did replace the timing chain tensioner, maybe you did not put something together correctly there and have some friction on the cam chain. Did you put the rear chain damper and dowel in correctly?

If you do have to pull the valve cover back off, I can say from experience that it is much easier the second time.

03silverbullet · Apr 9, 2008

I brought my bike to the shop to have them replace the cam chain tensioner awhile back, and some how the timing was altered.

The bike ran poorly afterward and after much arguing, the shop looked at it again and fixed the problem.

FJRMGM · Apr 9, 2008

sounds like timing to me.

HaulinAshe · Apr 9, 2008

It is possible to accidentally alter the valve timing with the tensioner removed. If you replaced the tensioner, I assume you also replaced the cam chain. If not and the chain has some appreciable age on it, do yourself a favor and change the chain while you are in there again.

+2 Sounds like timing to me.

salan10 · Apr 9, 2008

It's easy for the timing chain to slip off the sprocket at the crank shaft end when the tensioner is loosened or removed. I know because I did it and my engine ran the way yours did until I went back in to fix the timing. So, check the timing I think you'll find that your chain skipped a tooth.

longnokr · Apr 9, 2008

BUT I DON'T WANT THE TIMING TO BE OFF!! Too bad..... it was. I took it back down tonight and it damn sure did move. I wouldn't have dreamed that carefully switching the tensioner would let enough slack in it to jump....but there's plenty!! It's amazing how good it runs like that, It still ran VERY well!! Thanks for the input fellas, I've got a great ride planned with the Hoons this weekend...now I'll be able to keep up!!

dcarver · Apr 9, 2008

longnokr said:
BUT I DON'T WANT THE TIMING TO BE OFF!! Too bad..... it was. I took it back down tonight and it damn sure did move. I wouldn't have dreamed that carefully switching the tensioner would let enough slack in it to jump....but there's plenty!! It's amazing how good it runs like that, It still ran VERY well!! Thanks for the input fellas, I've got a great ride planned with the Hoons this weekend...now I'll be able to keep up!!

Scary, since I'm seriously thinking about doing my first valve adjust at home.. Pay attention to details, eh?Any tips for the rest of us as to what happened?

jeremyr62 · Apr 10, 2008

dcarver said:
longnokr said:

BUT I DON'T WANT THE TIMING TO BE OFF!! Too bad..... it was. I took it back down tonight and it damn sure did move. I wouldn't have dreamed that carefully switching the tensioner would let enough slack in it to jump....but there's plenty!! It's amazing how good it runs like that, It still ran VERY well!! Thanks for the input fellas, I've got a great ride planned with the Hoons this weekend...now I'll be able to keep up!!

Click to expand...

Scary, since I'm seriously thinking about doing my first valve adjust at home.. Pay attention to details, eh?Any tips for the rest of us as to what happened?

Did it jump the camshaft sprocket(s) or the crank? If the crank that could be a problem when shimming cos I would normally cable tie the chain to the camshaft sprockets to maintain timing at the top end but if there is enough room around the crank then this isn't going to work. (Fortunately at my last valve check all were well in tolerance so I haven't had to do this yet for my FJR)

longnokr · Apr 10, 2008

I didn't have to make any adjustments either, they were all fine. I just replaced the tensioner for preventative maintenance. I pulled it out and put the new one in without moving anything. Evidently the slack drooped under the crank sprocket and grabed the next tooth when I installed the new one. I turned it over by hand but didn't re-check marks cuz most automotive chains I've delt with won't move without sprockets being removed. But, all's well and a good lesson learned. I don't see how it would be possible to safely change the tensioner only without pulling the valve and timing covers to verify the marks are on.

dcarver-It won't be an issue if you have the covers off as you will to check your valves, just be sure and check the marks after you replace the tenssioner...if you do!

Geezer · Apr 11, 2008

longnokr said:
I don't see how it would be possible to safely change the tensioner only without pulling the valve and timing covers to verify the marks are on.

I have been thinking about this. Pulling off that valve cover is a pain in the neck. I don't think the chain will move from the cam sprockets because they are on top and gravity is on your side.

If you stuff a rag or something between the bottom of the crankshaft gear and the case it should hold the chain on that lower sprocket while you replace the tensioner.

Another option would be to hook a spring on the chain itself to keep tension on the back side of the chain loop while the tensioner is out.

If you're going to pull the valve covers to check the valves then I agree with Haulin' Ashe's advice to replace the chain along with the tensioner. I will do that next time I have my valve cover off.

jeremyr62 · Apr 11, 2008

"If you stuff a rag or something between the bottom of the crankshaft gear and the case it should hold the chain on that lower sprocket while you replace the tensioner."

Is this possible?

Geezer · Apr 11, 2008

jeremyr62 said:
"If you stuff a rag or something between the bottom of the crankshaft gear and the case it should hold the chain on that lower sprocket while you replace the tensioner."
Is this possible?

Well, there is a sensor in the way, but you should be able to get a rag in towards the front to hold it. I like the spring idea better. Maybe tie a wire around the rear chain guide and chain then hook a spring to that wire.

longnokr · Apr 12, 2008

Yes, if your going to pull the chain cover, it would be easy to hold the rear chain guide in place with something.....that would definitely be the easy and safe way to just change the tensioner, good idea!!

vabrzn · Apr 14, 2008

I haven't messed with the valves or camchain on the fjr yet, but on engines which I have, I put a paint mark on each sprocket and a corresponding paint mark on the camchain before I remove anything. I can easily see if something ain't right when I'm done.

Geezer · Apr 14, 2008

vabrzn said:
I haven't messed with the valves or camchain on the fjr yet, but on engines which I have, I put a paint mark on each sprocket and a corresponding paint mark on the camchain before I remove anything. I can easily see if something ain't right when I'm done.

Yes, or even better, a tiewrap to hold the chain on the cam sprockets. The problem is that it is a PITA to pull the valve cover to access the cams so you don't want to do that unless you are checking the valves clearance.

Lost about 10 HP after valve check?

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