|
|
Post by 90GTVert on Jul 7, 2006 23:25:07 GMT -5
I've edited this post because I was wrong about the type of carb adjustment on this model. Most carbs require you to turn the mixture screw IN to lean the mixture, but some (this one included) ar the opposite. The mixture screw in this case is adjusting the air and not the fuel like most. So, to richen the mixture, you turn the screw in (clockwise) and out to lean it. Sorry for the mix up. Stan
For those with a Tank 250, Roketa 250, Viva 250, et al, there IS an air/fuel mixture screw on the carb. I figured that since I couldn't see it, they must have plugged it, but when I removed the carb it was clearly visible, but very hard to get to. The screw is under the carb and only about 3/8" from the manifold. You would need to remove the air box to get to it. I found that the main jet is a 110 and pilot isn't marked, but by comparing it to a 35 and 38, I'd say it's a 38. The reason I was looking for this information is that I replaced the air box with a foam filter, causing it to run a bit lean, especially on the low end. I turned the screw out 1/2 turn and installed a 120 main jet and the problem is gone. If I'd had a 40 pilot jet, I'd have installed that too, but I'll have to order one to try. Anyway, I thought some of you might want to know the adjustment does exist.
Tomorrow, I hope to install and balance the new larger front tire and see how close I get on the speedo correction. It looks like the OEM tire is about 18" diameter and the TT150 is about 20" diameter. The 130/70 I have is around 19" so we'll see how it works. I may not be ambitious enough to do the rear right away, but I do have a 120/90 to replace the 110/90 that came on it.
Next week, I'll probably be test fitting a Kevlar belt and examining the rollers to see what's inside the variator. Stan
|
|
|
|
Post by scooterollie on Jul 8, 2006 8:21:39 GMT -5
Stan;
Great! Thanks for sharing that info. I was wondering about an adjustment screw and also thought it might be plugged. I would like to try backing mine out 1/8 - 1/4 to check the difference. A plug read shows it to possibly be a little on the lean side but I am not certain I have enough miles on the plug to get an accurate read. Don't seem to have any problems.
I had plans for more extensive mods on my 150 but think I will just leave this one stock for now.
My 4.00 X 12 front tire is 20". I am also interested to see what you find inside the variator.
|
|
|
|
Post by 90GTVert on Jul 8, 2006 8:53:39 GMT -5
I've been taking pictures of these things as I go, but I just haven't had time to write up any articles on them yet. As soon as I can clear some time, I'll get to that so that some of this stuff will be clearer.
I have some Polini Kevlar belts on the way to test for fit. I think the stock belt will be much better than the OEM belt on the 150, but I want to have replacements available when people want spares. So far, I have not found anyone carrying the OEM Bando belts in the right size, so I'll see how these work out.
Once I have the variator weight information, I want to replace them with sliders to see how they do. The power range on the 250 is very good, so I think the stock weight would be just fine, and I doubt there is a big advantage in changing the weight of them.
I was somewhat surprised at the main jet size being 110 since the 150 uses a 107, and this is a very slight difference. I forgot to measure the venturi size when I had the carb off, so I'm not sure how it compares to the 150's 24mm carb. I suspect it isn't a lot bigger though. I may try installing a 32mm carb on this one in time just to see how it works. I wouldn't mind getting rid of some of the extra plumbing they have on the OEM carb.
I really hope someone comes out with a better intake manifold soon. The OEM one is similar in construction to the one on the 150, and they are really prone to cracking from heat. Stan
|
|
|
|
Post by Jacine on Jul 8, 2006 9:57:29 GMT -5
The Keihin carbs use a 108 in the Helix, and a 110 main in the V3. The pms screw is also on the under side near the manifold. There is a carb tool, long right angle screw driver that can be used to adjust it without pulling the carb.
What plug size is being used?
Found mine to be one size hotter a 7, not the 8 in the manual, and pms was 3 1/4 turns out, not 2 1/4. Plug runs fine, and seems to boost power with the setting, although I loose gas mileage.
|
|
|
|
Post by Jacine on Jul 8, 2006 9:59:08 GMT -5
When the intake manifold is just a round tube shape, you can make your own from auto heater hose or similar rigid hose. Just cut it to fit.
|
|
|
|
Post by 90GTVert on Jul 8, 2006 11:04:22 GMT -5
The manifold is a flange base to the head and spigot to the carb. I really should have pulled it off, because I think the MRP aluminum manifold may bolt up in it's place. You wouldn't be able to use the OEM snorkle, but there is plenty of room to use a foam filter directly on the carb intake side. The OEM manifolds are aluminum with rubber molded over them to form the spigot end. The problem is that the Chinese rubber products don't hold up to heat so they become brittle and crack.
The stock plug is a DPR7EA-9 and the mixture screw was turned out 2 turns from the factory. I went to 2-1/2 and it seems about right. You could get to the adjustment with a very small stubby screwdriver, but the air box makes it almost impossible to see it. I've switched to an Iridium plug and it did help smooth the idle on it. Stan
|
|
|
|
Post by 90GTVert on Jul 15, 2006 21:23:21 GMT -5
Well, I opened the variator on the TT250 to take a look at the arrangement and inspect the weights. The variator is larger than the 150 of course, but it's also constructed differently. It has a rear cover that is held on with 3 machine screws, and the spacer in the center is splined to fit the drive shaft.
Probably the most interesting thing I found was that either the weights were crappy when installed, or they are wearing extremely fast, and have numerous flat spots. I just ordered a high accuracy gram scale, so when it arrives I'll get the weights, but I suspect they are either 19 or 21 grams. They use the same size weights as the Kymco 250's.
I also ordered an assortment of sliding weights to try to see if weight tuning has any benefit on these and also to check the durability of the sliders in this engine. Hopefully, they will show up so I can test them for the rest of you that will probably be experiencing the flat spots before long.
I should be installing the 32mm carb in about a week, then I'll move to the weights when everything is here and ready to go. Stan
|
|
|
|
Post by Jacine on Jul 15, 2006 21:52:19 GMT -5
You can weigh the rollers at the local supermarket, if they have an electronic scale by the produce.
|
|
|
|
Post by scooterollie on Jul 16, 2006 20:41:42 GMT -5
Stan;
Interesting news about the rollers. I have followed posts about variators but have not yet gotten into one. I purchased a gram scale last year so I will be able to weigh the rollers at home. Do you prefer the sliding kind to the round kind? From what I have read, I don't think I will spring for a racing-style variator, just fine tune the O.E.M. one.
|
|
|
|
Post by 90GTVert on Jul 16, 2006 21:10:46 GMT -5
I really do like the sliders better. In fact I only ordered sliders for the 250. I think there is one replacement variator available for the 250, but it's pretty expensive. I really like the Dr Pulley variator for the 150's and if they come out with one for the 250 I'd give it a shot. I'll post what the weights are when I open it back up. I really can't believe they have these flat spots in 350 KM, so I suspect they are not made as smooth as the should be from the factory. I'll be interested to see if this is an anomally or typical when someone else opens theirs up. Stan
|
|
|
|
Post by 90GTVert on Jul 21, 2006 0:00:10 GMT -5
I've edited my original post on the 250 carb adjustment because I gave bad information. The carb used on the 250 has the mixture screw adjusting the air side of the mixture rather than the more common fuel side of the mixture. So, if you turn the screw IN you are making the mixture richer (cutting back on the air) and OUT will lean the mixture (increasing the air). Sorry about the mistake.
Since I'm removing this carb anyway, I'm going to use a conventional adjustment carb. Stan
|
|
