Roketa Slow to Accelerate and Reduced Top Speed By ryand9 (Read 10,685 times)

[ryand9]

I own a Roketa that I just recently bought "new" that was manufactured in 2008. It is an MC-74-150. The 150cc engine had no issues accelerating up to or maintaining 60 mph until recently. I was at top speed when I went down a hill and the speed increased to almost 70mph. I came to a stop light at the bottom of the hill and when I accelerated away it was very slow. Also, it will only get up to 35-40 mph after a very long straight run. The tach reads between 3500-4000rpm and the engine does not rev up as I accelerate. It has no problem starting and the engine sounds normal. When I raise it on the center stand the engine will reach 6000rpm since there is no load on the drive wheel. It just won't accelerate like it once did and the top speed has been greatly reduced. The seller has told me to clean the carburetor and replace the CDI box, both of which have been done and the same issue persists. Any advice is greatly appreciated!

[sunlproblems]

sounds like rollers shifted in the track when you went that fast over the engine the clutch had the belt check that out

[sprocket]

I agree you need to take the CVT cover off and see what is happening.. likely rollers as sunlproblems suggested

[sunlproblems]

also could be the belt

[Jon C]

I just had a similar problem since I've been messing with my variator weights. Turns out the last 2 of my "Variator Glide Keys" (spacers) went missing or shreded, leaving my variator locked and the rollers not moving at all.

It's a 5 min job to check out the above suggestions.

Let us know what you find.

[ryand9]

Thanks for the tips. Once I get ahold of a spanner wrench I will let you know what I find.

[Bashan]

You don't need a spanner wrench. Go to just about any hardware store and get a strap wrench. Put it around the outside drive pulley and pop the nut with an impact wrench. It's quicker, easier, and you'll stand a lot less chance of harming the variator. Look in the CVT section of our library and you'll find at least one video on how to do this. Rich

[sprocket]

Spare the strap wrench... spoil the child...

Seriously... you need the right tools for the job and they are a strap wrench and impact wrench.. I also like a torque wrench to get the variator nut torqued to spec.. otherwise you will drive the kick start gear up the tapered shaft and you will never get it off.. should you need to rebuild the engine or replace the crank seal...

Rich is on his game today!

[ryand9]

I got ahold of a spanner wrench and was able to verify the rollers were moving freely. After inspecting them I reassembled and the issue persists. Is there an easy way to tell if my belt is stretched? I sent a video of me flexing the belt to the company that sold me the scooter and they said it was within spec. (however I don't trust their opinion) The last recommendation they gave me was that I need to change the oil and adjust the valves. Is it possible the valves could cause a problem like this, and after under 400 miles?

[sprocket]

Sure.. adjust the valve gaps... just to rule them out.....004inch intake and .005inch exhaust

You probably have a tight exhaust valve... you will need to do then at 800 miles so might as well adjust them now...

[ryand9]

Now we are getting into new territory for me. I have a pretty good video on how to adjust them and I know I can do that, but I don't know the best way to get to the valves. Any tips?

[sprocket]

Varies on every scooter.. on mine I can remove a panel under the front of the seat and get to them... Other you can work at them by removing the seat tub, on others the side panels need to come off...

[mapbike]

An issue with the valves was my guess as well, what made me think this is when you said that it only revs to 6000 RPM's with the rear wheel off the ground, if it were an issue with the variator or clutch it would still hit 8000+ RPM's easy with the rear wheel off the ground.

I went through a simular issue one time on a 50cc scoot that belong to one of my brothers, power just kept falling off until finally it wouldn't even start & run, I adjusted the valves and it started right up and ran like new, it had almost 3000 miles on it when all this started happening to it, I'm surprised it lasted that long because the valves had never been touched on it.

Anyway, set those valves and good luck.....hope it runs like a champ when you're done.

I also have a 2008 MC-74-150, great scoot! just set the valves on mine last week and it pulls better and revs better on the road now, mine has 2100+ miles on it now.

Peace, map

[mapbike]

Aug 4, 2011 12:16:57 GMT -6 ryand9 said:

I don't know the best way to get to the valves. Any tips?

Since I have a Roketa MC-74-150 I can help you out with this one.

raise seat, take out the storage compartment, lift the floor mat off, remove the 2 screws that hold the vented plastic cover that is directly under the front part of the seat, remove the cover, now if yours hase the air filter box that is under the seat you will be able to get to all of the 10mm bolts that attach it to the frame, remove all of the bolts, should be 4 if I remember right, remove the hose that goes from the air filter box to the valve cover on the engine, and now with a flat blade screwdrive loosen the hose clamp that clamps air filter snorkle onto carb., now remove air filter box.

Now you should be able to get to everything that you need to get to inorder to set the valves, now all you need to do is remove the valve cover and follow the direction for setting the valves on your scoot, very easy proccess only take a few min. and you will be putting all the plastic back on and be ready to start-er up.

hope this helps, I know it seems a bit chopped up but this all you need to do to get to the point of removing the valve cover.

Peace, map

[ryand9]

The description was great, thank you. I was able to adjust the valves (they needed it, they were closed much more than .004 and .005 when fully open). However, the issue persists. Still slow to accelerate and tops out around 35-40mph. Any ideas of what I should try next?