Top speed loss.

Irishrover · Post by **Irishrover** » Thu Oct 22, 2009 6:37 pm

My top speed is getting worse, now struggle to get 50mph.
Any suggestions as to what could be affecting this, maybe needs a new belt?

Post by **Lostmycage** » Thu Oct 22, 2009 7:08 pm

Made any changes lately?

Irishrover · Post by **Irishrover** » Thu Oct 22, 2009 10:12 pm

Lostmycage wrote:Made any changes lately?

Only change has been to put 6 11g sliders in and removed the 3 13g sliders I had in. New front disk, rear tyre and rear brake pads.

Post by **Lostmycage** » Fri Oct 23, 2009 2:26 am

Hrmm... unless you have clearance issues with the pads rubbing, then the 11g sliders aren't heavy enough to put the variator in the outter most gearing. That kinda goes against what's generally accepted as perfect for the 125cc engines, though. Is it at least quicker?

What's your belt's width at? If it's too far below spec, then it also won't get to the outer most range of the pulley.

santa · Post by **santa** » Fri Oct 23, 2009 3:47 am

Have you loosened up the valves. I found that making them slightly loose I get higher top end in the summer.

Post by **Lostmycage** » Fri Oct 23, 2009 3:56 am

Ha, wow! I found that tightening them up give me more peppiness. Haven't really tinkered with them for top speed.

That does bring to mind a valve adjust. If you haven't checked them in a while, it'd be a good way to insure that it's within spec.

Good call Santa!

jfrost2 · Post by **jfrost2** » Fri Oct 23, 2009 4:05 am

Slightly tight valves can give some pep, too tight then it becomes dangerous to the engine.

Post by **Lostmycage** » Fri Oct 23, 2009 4:21 am

I'm talking .01mm tight. Still sorta within spec, just tight.

Kaos · Post by **Kaos** » Fri Oct 23, 2009 1:34 pm

Lostmycage wrote:Ha, wow! I found that tightening them up give me more peppiness. Haven't really tinkered with them for top speed.

That does bring to mind a valve adjust. If you haven't checked them in a while, it'd be a good way to insure that it's within spec.

Good call Santa!

Yeah, tighter valves should increase speed, as the valves can allow more air in. Loose valves should always hurt performance, but like jfrost said, too tight can get the piston and valves to kiss and make nice. Not so nice for you though

santa · Post by **santa** » Fri Oct 23, 2009 4:37 pm

When I first got my Blur I kept getting lower and lower top end speed.

Since I bought it used, it had been sitting for two year with 20 miles on it, it had never had the valves adjusted after the first couple of hundred miles. My friend suggested this and pointed out that the valves can burn out if they are too tight.

Post by **Lostmycage** » Fri Oct 23, 2009 5:04 pm

I agree. Too tight will burn them out. Too loose will wear them out. Either way, a really good place to start is .08mm (recommended spec).

Just out of curiosity, what are yours set at Santa? Did you compare the loose setting to the spec setting or was it an improvement over the unadjusted/original condition?

santa · Post by **santa** » Fri Oct 23, 2009 10:54 pm

If I remember correctly I set it with a .08 tool, but just barely snug. However, you can hear that it is a bit loose when it is running.

When I tightened up just a bit to get rid of that sound I lost the top end and really could not use it on the freeway, which is the main way to get across town here in the suburbs.

I am really looking to get a SYM RV250 because I really don't have the roads around here that could take advantage of the Blurs "Gifts".

Irishrover · Post by **Irishrover** » Sat Oct 31, 2009 8:14 pm

Lostmycage wrote:
What's your belt's width at? If it's too far below spec, then it also won't get to the outer most range of the pulley.

Just measured the belt width today and it's 19mm, only lost 1mm since new. Changed back to my 3x13g & 3x11g slider setup, didn't like 6x11g.