losing power in 5th gear

[Damon001]

Hey, i bought a lexmoto adrenaline 125 for christmas. I was going down a road and no one was around and i hadn't felt what power the bike had yet (not that it would have that much anyway) so i went through all the gears on this road and noticed in gear 5, at about 8k rpm's the bike started to lose power and drop in revs, think its called bogging down or something? correct me if im wrong. But yeah, im not sure on what to look for or anything. Any advice would be grateful and thanks in advance!

[Baffler186]

How fast were you going? You're never going to have much acceleration in top gear on a learner 125. Are you sure it was bogging, or was it just going baaawwwwww and not really accelerating?

Get out onto a fast road (60), rev it up through the gears and only change into 5th when you're up to 55ish. If it suddenly loses power and the bike lurches forward, report back. It still won't accelerate much at that speed but you should be able to maintain 60.
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Current: 2009 SV650 S, 1990 Kawasaki GT550
Previous: 2009 CBF125, 1998 GSF600, 2004 FZ6 Fazer, 1978 CB400a Hondamatic

[Damon001]

[doggone]

Top gear can be a bit like an overdrive on a lot of small bikes,and you might only get to use it with a tail wind or long slight downhill especially if you are more than about ten stone
Maybe someone changed the sprockets in an effort to increase top speed?
If it doesn't get any worse that's probably just how it is.

Some cars are rather similar and you can only get into top when at a decent cruising speed about 70mph - better economy on motorways.

[Damon001]

[Rogerborg]

Without riding it, we can't be sure, but it's possible that you're just being phucked by physics.

<Tef>

When you changed up to 5th, the revs had to drop to match whatever road speed you were doing. Problem is, your engine makes its peak power at 9,500 rpm. If it wasn't making enough power at 8K to overcome your drag (which is related to your velocity squared), then slow down you shall until power = drag.

Rev it right out in 4th and only then change up. Other than that, you could consider tinkering with the gearing. Shortening it (going down a tooth on the front sprocket) might make 5th more usable, at the cost of requiring more frequent gear changing - and you'll always be in the wrong gear anyway, read on.

Conversely, going up a tooth on the front might extend the speed of 4th, while hopefully still leaving it a shorter and more usable gear than your stock 5th, which you can just forget about. No guarantees, it's not an exact science, and the slightest incline or headwind will still stuff you anyway.

</Tef>

The bad news is regarding that Suzuki engine of which yours is a (carbed) copy. Previously, I wrote, and still stick by:

[kgm]

On my CG125 I hardly ever use 5th unless on a level road with no wind and in a straight line or it starts to slow down a bit. It's only really any use as an overdrive gear. Slightest hill or strong wind and it begins to struggle. You really have to rev it right up high in 4th before changing.

Mine isn't as bad as what you're describing but I suspect it's for the same reason rather than a mechanical issue.

[thx1138]

the vanvan 125 was like that in 6th gear

the 200 only has 5 gears

[NutsyUk]

This is similar to what what happening with my XTRS...

Turned out the suggestions of tight tappets was correct. Its running a lot better...

I know we have different bikes. but maybe its the same problem? The tappets too tight/closed...

As for gears... I find myself using 5th gear a lot... even at lower speeds like 30-40 as my bike plods along at lower revs happily and its more efficient with the petrol... Does that put too much strain on parts of the bike?
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Yamaha FZ8/Fazer800 (split headlight one) 2014, gingerly getting used to the massive increase in HP and not killing myself in the process! That was easy to get used to.
Kawasaki ER6F 2007 650 Gonna sell as a project bike!
Lexmoto XTR S 125 Sold!

[doggone]

[Rogerborg]

Given how little "response" I could batter out of that engine (in genuine Suzuki form), you might be as well just nursing it along in 5th.
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Dave70]

[Dimerz]