|
Post by oldgeek on Aug 14, 2022 13:23:07 GMT -5
I have no experience with the VHST, however with the PHBG I once had an issue where the tab on the float that interacts with the valve was binding on occasion. I may be totally off base here but I dont see how fuel level in the bowl is super critical. I feel like as long as the jets jets stay submerged in fuel and the fuel level is not so high that it constantly interferes with the venting you should be good Another thought, how much pressure from the fuel tank would be needed to overcome the fairly light pressure the float puts on the float valve when it is closed. Put another way is it possible the fuel weight in your larger than normal tank is putting more pressure on the float valve than it can hold back? Maybe run just a 1/4 tank of fuel for some tests. I am going to search for some pictures of the VHST, I would like to get a good look at the internals to see what may be going on.
|
|
|
Post by 190mech on Aug 14, 2022 15:58:01 GMT -5
Looks like your test setup has the carb level and the fuel height is waay up there! When the carb is tilted the level changes also.. The float level is VERY important as the standing fuel in the atomizer nozzle allows the airflow to pick up the mixture sooner with a high level and later with a lower level..When the carb is canted, the level can actually start dribbling out of the idle circuit all the time causing stupid stuff to happen..Thats why I think canting a float type carb designed to run level is a BAD idea!! Back to your test with it level, it is way too high in the pics..So the float needle/seat is leaking,float is fuel logged,or linkage is binding.. Ideal fix is to get the float level in check and reduce the cant of the carb as much as possible...
|
|
|
Post by fly on Aug 14, 2022 17:06:42 GMT -5
For me, that's why I tried to get mine sitting pretty level. As expressed in my own thread I'm not sure about the intake length. But it seems to me you're going to be mounting at a high angle to get close to the reeds, or you're going to add some length to level it out.
A longer intake should be a softer hit, pull real good through the mid-range, but won't be as good up top. I'm juggling all this right now. It's all theory for me. In the end I can't tune until I've got a running bike, but I'm trying to design with the best of my woefully inadequate knowledge to reduce the amount of futzing I'll need to do later.
But I guess my point is, it's deciding on where you want to land with compromises. Tune for where you do most your riding has always been my philosophy, while others tune for max top speed. IMO, max theoretical power doesn't mean max riding experience.
Incidentally, do you happen to know the crankcase/cylinder volume ratio with the RC1 cases?
|
|
|
Post by 90GTVert on Aug 14, 2022 17:38:13 GMT -5
For me, that's why I tried to get mine sitting pretty level. As expressed in my own thread I'm not sure about the intake length. But it seems to me you're going to be mounting at a high angle to get close to the reeds, or you're going to add some length to level it out. A longer intake should be a softer hit, pull real good through the mid-range, but won't be as good up top. I'm juggling all this right now. It's all theory for me. In the end I can't tune until I've got a running bike, but I'm trying to design with the best of my woefully inadequate knowledge to reduce the amount of futzing I'll need to do later. But I guess my point is, it's deciding on where you want to land with compromises. Tune for where you do most your riding has always been my philosophy, while others tune for max top speed. IMO, max theoretical power doesn't mean max riding experience. Incidentally, do you happen to know the crankcase/cylinder volume ratio with the RC1 cases? Sorry, not a clue on the primary compression. I'm fine with peaky with this thing. It stays in the powerband fairly well when on the throttle and hard hitting is pretty fun. I don't feel like I'm lacking any essential pulling power when I get the wheel off the road at part throttle when trying to get going around turns sometimes. It's certainly not smooth delivery, but I think if you build something like this and want a nice calm ride... you've built the wrong engine. Ryan seems to struggle just a bit more with just moving without the front being light, but I think he is using a throttle with very quick action. Mine takes a 1/4 turn and I can ease into it without issue most of the time, so I'd say that may be a good move for a simpler ride. I don't see the need for a quick throttle here unless you're getting really competitive drag racing. I have to roll in anyway from a stop. I could see it as an advantage once I start moving to get to WOT a little quicker. I can snap it open quickly enough to wheelie (sometimes more than I want) from 25-30MPH when it's running strong so I'm not sure how much more response you'd want. I still think the angle can be OK, but I have to get it to stop filling the bowl all the way. That's not going to be good in any orientation.
|
|
|
Post by fly on Aug 14, 2022 19:23:31 GMT -5
Nothing calm about 94cc at 13-14k rpm! 😅😅😅
|
|
|
Post by 190mech on Aug 14, 2022 19:38:23 GMT -5
There are 'downdraft' float carbs, check out the YD30,its a yoshi knockoff that is a bent PWK...
|
|
|
Post by Lucass2T on Aug 14, 2022 23:21:44 GMT -5
Time for a Keihin ta-09, they're like john said some sort of semi down draft unit. You saw them come around from time to time in the eu-scooter racing scene back in the days. They came originally on nsr400's.
|
|
|
Post by captincvmn on Aug 15, 2022 6:08:02 GMT -5
Tillotson
|
|
|
Post by 90GTVert on Aug 15, 2022 13:13:13 GMT -5
I am going to search for some pictures of the VHST, I would like to get a good look at the internals to see what may be going on. Maybe these will help. Not so much for real internals, but at least you can see the float setup. I took the carb off to see why it was pouring fuel suddenly. I said I was over it Sat night. I guess I really was. The bowl bolt was in there, but not tightened. 🤦♂️ I was looking for parts and found that there are supposed to be 3 different weights of floats. The part number is 15760.3, .4 or .5. .3 = 4.0g .4 = 5.2g .5 = 3.6g I’ll check mine and the needle and seat while it’s on the bench.
|
|
|
Post by oldgeek on Aug 15, 2022 18:55:06 GMT -5
Great pics! Interesting setup compared to the limited number of carbs I have experience with. Strange that the main jet is pointed in the opposite direction of fuel flow compared to other carbs such as the PHBG. There are four slits in the bowl near the main jet holder hole, do they index with the feed holes in the main jet holder or just there to make a sump area? Also noticed the main jet sump is off center of the bowl, to the filter side. It would have been nice if it were towards the motor side since the carb is tilted that way.
The two independent floats are also interesting, seems to be tricky bending each arm to make them the same level. I noticed one of the pivot posts appears to be machined just a bit on the inside of it, however the post on the starter jet side appears to be just cast and no machining. Is there any possibility something is catching the pivot there? Possibly some very thin plastic washers placed on each side are in order.
|
|
|
Post by 90GTVert on Aug 15, 2022 23:23:17 GMT -5
I don't think the holes in the main jet align with the ditches in the bowl.
I weighed the floats and they're 3.8g. They're labeled 3.6g. It seemed odd to me that both would be off by pretty much the exact same amount though. I checked calibration of my scale a 100g weight and it passed. I had a couple of brand new sets of 3.5g DrPulley sliders around so I weighed those. 3.45-3.47g. Definitely not showing 0.2g heavy. Maybe there's a good reason, but I'd think if plastic were soaking up fuel or something that it should be a little less equal side to side. Maybe not. If this is indeed incorrect, that could account for at least some of the high float height.
I intended to test the needle and seat with a vacuum tester. Didn't get there. I had a once close friend that I haven't seen in 16-17 years get in touch and wanted to come up to catch up. In conversation I found out that he recently bought an '88 Mustang GT with a carbed 351W and wants to add nitrous, fix up a few things, and take it to the track. He's having some stuff done, but maybe I can help do a few things so he's a bit more comfortable working on his own car. We know it's more satisfying to DIY... even if there may be a few expletives in the process. We'll see. If nothing else, I showed him the dragy so now he wants to come up and try a few test runs in the near future. 👍
|
|
|
Post by Lucass2T on Aug 16, 2022 2:43:04 GMT -5
...he recently bought an '88 Mustang GT... Those fox bodies are pretty rad!
|
|
|
Post by 90GTVert on Aug 16, 2022 11:24:50 GMT -5
I did the vacuum test for the float needle/seat. Vac brake bleeder attached to the carb's fuel inlet. Carb upside down so fuel passage should be sealed. It held ~10psi. Didn't wait like a leak test on cases, just made sure it was OK for a minute. Then I sprayed it with some 50/50 Simple Green/water mix. No bubbles. Seems good enough to me, so I guess I'll order new floats. Just need a few to look around and see if I can get them cheaper than $30 + S&H. $40+ for 7.2g of plastic kinda sucks. I did take another test ride real quick. Still breaking up bad off the line and after I hold the throttle for a bit (maybe by 50ish) it warbles like it's way rich. EDIT : $26.17 total for 2 floats. www.ebay.com/itm/175323976273
|
|
|
Post by 190mech on Aug 16, 2022 18:24:15 GMT -5
Sorry for thread jacking! Here are a few 'twisted' carbs from a file posted by Frits Overmars a few years back,,
|
|
|
Post by 90GTVert on Aug 17, 2022 11:57:38 GMT -5
The water pump shutoff on me a few times trying to do tests because of high voltage, so I wanted to try out a new reg/rec. Months ago, I was told about a Tomos moped regulator that worked for someone else to control voltage on their MVT setup. From "Mike Kuijpers" via YouTube : "Hi Brent, love the vids, i was wondering if you still have the overcharging issue you had earlier when using the MVT ignition system, Recently i installed MVT system on my Piaggio, i tried a whole bunch of regulators but also had the same issues you had, After a bunch of testing came up with the best solution for me, i used a Ducati 230844 regulator, it originally was used on a Tomos moped but worked perfectly on the MVT system it charges around 14volts! I can provide some more info if you would like!" "The only difference is that i have the premium version of the MVT ignition system, i assume that the output voltage is the same between all the inner rotor systems, I hooked mine up 1. Pin yellow or white(i don’t remember)2. Pin battery negative 3. Pin blue from MVT 4. Pin battery positive" So I picked this up some time ago : www.treatland.tv/ProductDetails.asp?ProductCode=tomos-a55-regulator-230844Even having his pinout, assuming 1->4 was L->R, I tried to use the diode test method from here : 49ccscoot.proboards.com/thread/410/testing-prong-rectifier-identifying-terminalsMy results didn't align with the anticipated test results though. I'm not sure if it's a different type of regulator or what. I could find things that seem to go along with the test, but the whole picture did not. Based on the diode test, I thought 1 & 4 were AC and neither matched up to + or -. I figured it would be easiest just to try the pinout mentioned in the comment... sort of. I don't have a blue wire on the digital direct like he has on his premium. I made up jumpers to go from my current connector to this for temporary testing and hooked it up this way : 1 & 3 : AC charging. Yellow and white wires. It shouldn't matter which is where AFIK. 2 : - 4 : + It kinda works. I can see voltage rise when revved. The problem is where it is limiting power. With no lights on, my batt voltage goes up to 12.4 and no higher. With my halo LED on and tail light, it goes up to 12.2 and no higher. With the headlight on it is 11.9 max IIRC. This is with the electric water pump running as well in all cases. This seems like something you'd use to power a light or accessory so it never got much higher than 12V, but it won't allow charging of the battery. I'd like to see 14-14.5V. I'm not really sure why the voltage changes depending on electrical load either. Normally, voltage goes to wherever the reg limits it or till you've maxed out available charging. My setup now goes way high... 16V and beyond at times. That's why the water pump shuts down. I'd prefer that to never charging though. At least I can turn on more lights when I need to keep it in check for cruising. WOT it may overcharge anyway. I don't think swapping anything around would do anything. From what I've seen in the past with reg/rec wiring, it either works or it doesn't. The 2 AC wires can be in either AC spot, but otherwise if it's wrong it won't allow charging at all. Not sure why the poster got 14V regulation and I don't. Maybe with no load it would do that, but that does me no good. I have at least a couple of different reg/recs around from various Chinese scoots. I may try to diode check them and hook them up to see if I can get anything better than the genuine Yamaha Zuma reg/rec is doing for me. It's done this since new BTW, and I did try a 2nd, so it's not just a faulty reg or I got 2 new faulty ones from Yamaha.
|
|