coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 26, 2019 17:51:58 GMT -5
I have a new belt that arrived today. I am going to install and update how that goes.
|
|
coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 26, 2019 19:17:14 GMT -5
The belt looks to be too wide and not long enough. Its sitting low in the clutch and high on the variatior. It may be an optical illusion but it seems that the belt overhangs the variator boss by just a little bit. You also aren't getting full travel on the variator as the red left on it shows. Installed the new (Gate Kevlar) belt I ordered a couple weeks ago to go along with the kit. Disappointment again as I lost 2 mph. The RPMs were at nearly 8000. Another disappointment is that the bike wouldn't run at all at first. I did some troubleshooting, changed the kit racing CDI back to the stock and it cranked first time. The new CDI has already quit on me. Back to the belt tho. The new belt appears to be exactly the same length but is ever so slightly narrower when compared to the stock belt. Being Narrow it seems that it is not getting pushed as high on the variator as the original belt. Still waiting on the compression tester kit to arrive. One thing after another and we are not making any progress.
|
|
|
Post by Happypancake! on Feb 26, 2019 20:52:02 GMT -5
Looking for belt travel all the way up on the variator. Options are to GET a shorter drive boss or shave down the nipple on the drive face a few mm. With either mod make sure you don’t take too much off as the nut will mess up the crank splines
|
|
coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 27, 2019 10:03:54 GMT -5
I can shorten an old drive boss this weekend and see if I can get the belt to travel farther up the variator.
|
|
|
Post by dexameth on Feb 27, 2019 10:31:10 GMT -5
The size of the belt has yet to be mentioned (or did I look over it??) so what was on there stock, and what Gates did you replace it with? You definitely are not getting full belt travel, the resting position looks normal but it is definitely not reaching the top. A long case 139QMB should use a 729x18x30 and I've seen some stock engines come with the limiting 723x18x30 belt. I've even played around with the 738x18x30 and found I love the longer belt (sits higher at resting, so take off is much better and wheelies are easier).
Let me know what you are working with here...
|
|
coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 27, 2019 10:36:08 GMT -5
The size of the belt has yet to be mentioned (or did I look over it??) so what was on there stock, and what Gates did you replace it with? You definitely are not getting full belt travel, the resting position looks normal but it is definitely not reaching the top. A long case 139QMB should use a 729x18x30 and I've seen some stock engines come with the limiting 723x18x30 belt. I've even played around with the 738x18x30 and found I love the longer belt (sits higher at resting, so take off is much better and wheelies are easier). Let me know what you are working with here... dexameth, Stock Belt is: ZIJINGANG VS BELT 729 17.7 30 Gates Belt is: GATES POWERLINK KEVLAR DRIVE BELT 729 17.5 30
|
|
|
Post by dexameth on Feb 27, 2019 10:45:08 GMT -5
The size of the belt has yet to be mentioned (or did I look over it??) so what was on there stock, and what Gates did you replace it with? You definitely are not getting full belt travel, the resting position looks normal but it is definitely not reaching the top. A long case 139QMB should use a 729x18x30 and I've seen some stock engines come with the limiting 723x18x30 belt. I've even played around with the 738x18x30 and found I love the longer belt (sits higher at resting, so take off is much better and wheelies are easier). Let me know what you are working with here... dexameth, Stock Belt is: ZIJINGANG VS BELT 729 17.7 30 Gates Belt is: GATES POWERLINK KEVLAR DRIVE BELT 729 17.5 30 Correct sizing. Did you find a little washer or shim in the vari when you took it apart? Also, could you measure the boss length?
|
|
coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 27, 2019 10:57:18 GMT -5
dexameth, Stock Belt is: ZIJINGANG VS BELT 729 17.7 30 Gates Belt is: GATES POWERLINK KEVLAR DRIVE BELT 729 17.5 30 Correct sizing. Did you find a little washer or shim in the vari when you took it apart? Also, could you measure the boss length? dexameth, No washer, spacer, shim in variator. I can measure the boss length when I get home from work and report back later today.
|
|
|
Post by dexameth on Feb 27, 2019 11:06:27 GMT -5
Okay, no problem. Looking over the build, everything seems legit except one thing: the clutch. Maybe it isn't allowing full belt travel? When you installed the 1.5k spring did everything go together fine? With what you've mentioned I don't see why this scoot shouldn't see 40mph easy, unless you have what fugaziiv mentioned: low compression. We've seen cheap heads with valves that did not seal against the valve seat creating blowby in the ports a and low power. I've gotten accustomed to lapping my valves before installing a new head.
|
|
coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 27, 2019 11:13:21 GMT -5
Okay, no problem. Looking over the build, everything seems legit except one thing: the clutch. Maybe it isn't allowing full belt travel? When you installed the 1.5k spring did everything go together fine? With what you've mentioned I don't see why this scoot shouldn't see 40mph easy, unless you have what fugaziiv mentioned: low compression. We've seen cheap heads with valves that did not seal against the valve seat creating blowby in the ports a and low power. I've gotten accustomed to lapping my valves before installing a new head. This evening I will be able to test compression and measure the boss length. I had no issues with the 1.5k spring install and all parts went together as expected. I will also check the spacing again at the rocker arms to ensure they are still gap'd correctly. Is this belt similar to what you have experimented with? Bando CVT Drive Belt 738-18-30 www.partsforscooters.com/106-120-Bando-738-18-30-CVT-Belt?sc=31&category=132537
|
|
|
Post by dexameth on Feb 27, 2019 11:16:39 GMT -5
Yup, that's the belt I used. The added length might actually go against what you are trying for. My experience was the 738 belt had snappier take off and less top speed, when the 729 belt had a bit slower takeoff and more top speed. 738 topped at 52 same day/weather/etc 729 topped out at 56
|
|
coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 27, 2019 11:20:26 GMT -5
Yup, that's the belt I used. The added length might actually go against what you are trying for. My experience was the 738 belt had snappier take off and less top speed, when the 729 belt had a bit slower takeoff and more top speed. 738 topped at 52 same day/weather/etc 729 topped out at 56 Dang! 52 or 56??? That's awesome! We just need to get to 38mph-40mph for safe travel with the flow of traffic to and from school.
|
|
|
Post by dexameth on Feb 27, 2019 11:22:43 GMT -5
Haha yeah, I have every mod possible thrown at this engine. Stroker crank, 52mm bore, taller gears, ported head with larger carb blah blah blah... I wanna help you reach that goal (and some hopefully!).
|
|
|
Post by fugaziiv on Feb 27, 2019 11:24:33 GMT -5
Yup, that's the belt I used. The added length might actually go against what you are trying for. My experience was the 738 belt had snappier take off and less top speed, when the 729 belt had a bit slower takeoff and more top speed. 738 topped at 52 same day/weather/etc 729 topped out at 56 Dang! 52 or 56??? That's awesome! We just need to get to 38mph-40mph for safe travel with the flow of traffic to and from school. To be fair, dexameth has what might be the beastly-est QMB street build in the US. I'd say it's certainly top 5 that I'm aware of. Matt
|
|
coachm
Scoot Member
All my friends have life goals, I just want to go faster
Posts: 24
Location: USA
|
Post by coachm on Feb 27, 2019 11:25:41 GMT -5
Haha yeah, I have every mod possible thrown at this engine. Stroker crank, 52mm bore, taller gears, ported head with larger carb blah blah blah... I wanna help you reach that goal (and some hopefully!).^^^^ thank you ^^^^ I appreciate all the help. Look for my update later this evening with the compression test and boss length. We will get there (and some0.
|
|