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No power under 7000rpm

Started by Fj1200buggy, February 11, 2017, 07:04:46 AM

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Fj1200buggy

The engine ran well, but after i replaced the carb diaphragms (jbm) and exhausts there is no power below around 7000rpm.
After 7000 it pulls extremely well.
I dont ride alot, but have cleaned the carbs and checked the fuel recently.
The new exhausts are maybe a bit more restrictive than the stock ones, they come off a Harley and I put them on to reduce noise. They are not straight through.
Any ideas?
Thanks, Erik.

mr blackstock

G'day,

I am not sure about the exhausts and the effect changing them might have had on the running, but regarding the carb diaphragms, after re-installing teh slides into the carbies, did you make sure the two little holes next to the needle were facing the engine?  The FJ1100 has the little holes, not sure of the 1200 does.  But installing the slides backwards might affect the running...

cheers, Gareth
Squeaky wheels always get the grease...

Yamaha FJ1100 1985

FJmonkey

If it ran well before the changes then one of the changes are suspect. What you describe sounds like the idle jets are clogged. Sitting for too long (more than 4 weeks) with the crappy gas here in the USA will cause the smaller jets to clog up. Running well in the higher revs is where the larger (harder to clog) jets kick in.
The glass is not half full, it was engineered with a 2X safety factor.

'86 Ambulance - Bent frame, cracked case, due for an overhaul
'89 Stormy Blue - Suits my Dark Side

Fj1200buggy

Quote from: mr blackstock on February 13, 2017, 05:18:29 AM
G'day,

I am not sure about the exhausts and the effect changing them might have had on the running, but regarding the carb diaphragms, after re-installing teh slides into the carbies, did you make sure the two little holes next to the needle were facing the engine?  The FJ1100 has the little holes, not sure of the 1200 does.  But installing the slides backwards might affect the running...

cheers, Gareth
Thank you very much!
They have a hole in front of the needle, 2 of them were the wrong way around, I fixed them and it pulls much stronger now and runs smoother!

Quote from: FJmonkey on February 13, 2017, 09:08:41 AM
If it ran well before the changes then one of the changes are suspect. What you describe sounds like the idle jets are clogged. Sitting for too long (more than 4 weeks) with the crappy gas here in the USA will cause the smaller jets to clog up. Running well in the higher revs is where the larger (harder to clog) jets kick in.
Thanks, it sits quit a lot, sometimes a few months between short rides, hopefully that will change....
I will clean the carbs again sometime as i feel it is still missing a bit of torque in the low revs.


X-Ray

I would think that putting a good fuel stabiliser/cleaner in your tank would be beneficial if the bike does sit for long periods of time. I only just became aware that Seafoam is available in Australia, bought a couple of cans and put approx 40ml per tank in both my bikes now.
'94 FJ1200 Wet Pale Brown
'93 FJ1200 Dark Violet/Silver
'84 FJ1100 Red/White

'91 FJ1200 Dark Violet/Silver ( Now Sold)
'92 FJ1200 Project/Resto Dark Violet/Silver (Now Sold)






For photos of my rear wheel swap, heres the link  https://www.flickr.com/gp/150032671@N02/62k3KZ

Pat Conlon

Ray, it that for hot weather storage, or cold weather?
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

X-Ray

Well everything I have read Pat regarding Seafoam is that users run a bit through the bikes and then store for the winter so to speak. A couple of things I have read over here is that ethanol blended fuels start to "go off" in as little as 4 weeks, where the premium unleadeds etc will go for much longer ( as in months ) before any noticeable changes occur. One reason I started to use a bit of Seafoam is my mate across the road with his GTS1000 Yam that very rarely gets ridden sat for approx 3 1/2 months, and when he went to start it, no go. Took us several days to get it to fire, and I reckon it was "stale" fuel, which the fuel injection system didn't like.

My bikes which might sit for a couple of weeks between rides get some treatment in each tank just to help keep things clean internally carb wise as well. Heard so many good things about this product, thought why not try it. :)

'94 FJ1200 Wet Pale Brown
'93 FJ1200 Dark Violet/Silver
'84 FJ1100 Red/White

'91 FJ1200 Dark Violet/Silver ( Now Sold)
'92 FJ1200 Project/Resto Dark Violet/Silver (Now Sold)






For photos of my rear wheel swap, heres the link  https://www.flickr.com/gp/150032671@N02/62k3KZ

big r

I have used seafoam for the last couple of years. My bike sat for a full season as I was working away from home. Last spring put the battery in and after a few shots at turning it over she fired. Rode her last summer and did not have an issue, she ran like a top . No hesitation and would rev right out. I think that stuff is great. We have 15% ethanol in our gas here. Big R

Bones

Quote from: X-Ray on March 15, 2017, 07:21:28 PM
I only just became aware that Seafoam is available in Australia, bought a couple of cans and put approx 40ml per tank in both my bikes now.


Where do you buy it Ray, might put some in my Suzuki.
93 fj1200
79 suzuki gt250x7


Too young to be old but old enough to know better.

X-Ray

I bought it from this ebayer Tony http://www.ebay.com.au/itm/SeaFoam-Motor-Engine-Treatment-Auto-Marine-Boat-Fleet-Gas-Diesel-1-can-16oz-AU/302252979203

Not cheap $25.00 per can compared to $1.50 I think the US guys pay  :biggrin: :biggrin:  but you don't use much so I think should last a while.
'94 FJ1200 Wet Pale Brown
'93 FJ1200 Dark Violet/Silver
'84 FJ1100 Red/White

'91 FJ1200 Dark Violet/Silver ( Now Sold)
'92 FJ1200 Project/Resto Dark Violet/Silver (Now Sold)






For photos of my rear wheel swap, heres the link  https://www.flickr.com/gp/150032671@N02/62k3KZ

Pat Conlon

1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3