Tri-z mod jetting issue

[tippmann]

Ok im desesperated right now about jetting.

The z: 1985 tri-z bored to second oversize .5(i think) , wrench report phase 2 , dg exhaust , 38mm miku tm (flat) open lid on air box, v-force reed cage. All bearing , Seal Gasket are new. COmpression 180 psi

Carb: setting right now are : 560 main ,q-2 needle jet , 50 slow, cant remember the needle but its the one that was comming with the carb.

Problem: even at 560 after a plug test at 5 gear wot then clutch+ kill switch spark plug are white + he spitting prestone a good shot. while im riding it he seem to cut a bit on every gear like if he miss gaz.(white plug confirm) but from 450 to 560 its the same deal happen.

So some peaple told me that he could pull some air within seal or somewhere else so I used break cleaner all over the head, reed cage , base of the cylinder and the sound didnt changed. I only have the seal behind the stator to look but hes new.

I had some Issue with my guy who made me the mod to port and head shaving. it ended that i had to put a thicker base cylinder gasket so it raised my port approx. by 0.008 '' My squish test:0.033'' compression 180psi

some told me that its look like you needle jet is too small so even bigger the main jet im stuck by the needle jet that why bigger jet do nothing

that or my port job is ''pass over'' (not sure how to say this but port too big and its bad ) But when i test the Z seem to pull right.

So i hope some1 here will have a good idea to help me there. and if i have to change the needle jet with what i have to switch a q-3 q-5 or switch to a bigger size in letter? like r-2 ?

p.s he dont smell prestone burned and i swapped my oil she had no pretone in it too but she was already dark... but since i rebuilded the bike its the first oil i putted in maybe its normal,.

[badass350x]

Sounds like you need a bigger main jet, if the plug is white on top speed plug chop, your running lean on your top end! Your needle is your mid range for the most part!!!

[badass350x]

Also double check your timing ..

[El Camexican]

I’m not saying this is your problem for certain, but I did see what I am about to tell you happen once...

A guy I know put a set of 40mm Mikuni RS Flat Slides on a 1200cc Kawasaki. He started with 140 Round jets (a very common jet for large 4 strokes, works in almost all conditions) The bike ran bad, really bad and the plugs were white as bone. His engine builder/tuner (who I still think is an idiot) had him running all the way up to 175, or 180’s with the same problem. These jets could have drowned a 1500cc Pro Mod, but they couldn’t feed the mild 1200 enough fuel.

In the end the problem was the size of the manifolds. They were eventually stock in diameter and just stretched over the 40mm carbs. What this did was put an obstruction between the draw of vacuum coming from the engine and the orifice of the main jet. Essentially it didn’t matter how big the jets were the engine couldn’t draw fuel up from the bowl.
In your case we all know a 38mm works well on a 250 Tri-Z, but being that my manifold already came somewhat modified I don’t know how much restriction a stoker has, so you need to take a look at this on your set-up. If the inner diameter of the manifold is smaller than the inner diameter of your 38mm carb I recommend you match it up before worrying about your main jet.

Once you are done I’d consider going back to a 480 or 490 and trying it. All other things being equal a modified engine will sometimes need a smaller main jet as the flow has improved to the point that the motor is creating more vacuum and drawing more fuel out of the same size jet.

Oh, and make sure your float is set correctly and is allowing the main jet to get enough fuel. If it is too low this could also be an issue.

[tippmann]

You make me think about my v force 3 cage the cage is in 2 part andthe second lower the size here a pic i found
http://www.google.ca/imgres?q=v-forc...16,s:141,i:145

think i had to remove this part ?

about the float high how can i set it ?

[El Camexican]

I don't have a V-Force cage, but someone here must. What size diameter is that round hole? What size is the hole in your rubber manifold? I don't do French, but it looks like the ad says "for an 85cc engine" Is your V-Force for a Tri-Z, YZ or IT 250 or something else?

[tippmann]

v303a for kx 125 04-08 wwith p682m petal who are softer ,, this set up used by some peaple here... but maybe i had to remove the second part that reduce the hole size.

[El Camexican]

Yea, I just went looking for a V Force for an old YZ and they don't list them. So again I ask "what does the opening of that hole measure? If it is less than 36mm it may be the problem. Also, did the cage come with a manifold, or are you using the stock Yamaha manifold?

[Mosh]

V force makes a larger stuffer for the Z cage. Typically we use it on the BB 310 kits. But maybe it may help you in this situation.

http://www.3wheelerworld.com/showthr...S-PAGE-4/page4

Now, awhile ago I told you I was concerned with your squish readings. I said nothing lower than .035" and, you would need race gas at possibly .045 of squish..Z's just dont like tight chambers. At least during all the testing I did, they didn't like it. It prevents them from over-revving something fierce. I am sure someone here maybe has an opposite opinion on that, but what works for one may not work for the other guy. Just too many variables from engine to engine.
I am not an expert on the issue, it is just what I noticed during testing of the domes for the coolheads.

Are you running race fuel at those readings on your engine? If not, you need to be IMO.

Lastly...I absolutely have no faith in a Mikuni Flatside carb..And I dont recall hearing many good reviews on them either. I would say you may be better off to go over to a PWK 38 mil.
Also look into the new Z billet intakes. They flow more, eliminate the boost bottle, and fit the larger carbs much better. They are available for purchase in the 3WW store.

I dont want you to buy parts you dont need, but I definately agree with the OEM intake boot being way to small for a ported engine built to breath. I also know that too tight of compression on certain engine designs inhibits top end pull. Lastly, there are better breathing top end pipes than a DG. The Phase 5 or Answer pipes seem to have a little more topend pull over a DG. The Dg will work ok for you but if you find a good deal on one of the ones I mentioned try it.

[tippmann]

Ill start by buying some octane this next monday i have sone test to do before buying part at high price again but about the stroker if the v force you grinded it ?

[tippmann]

If i put back the hold reed cage who dont have the stuffer or i simply remove the stuffer off the v force cage then done a wot test with my 560 main jet who is probably way too big ill see if the stuffer is too small ?if my spark plug getting hella wet after this try it mean that im stuck by the v force stuffer size

[El Camexican]

If i put back the hold reed cage who dont have the stuffer or i simply remove the stuffer off the v force cage then done a wot test with my 560 main jet who is probably way too big ill see if the stuffer is too small ?if my spark plug getting hella wet after this try it mean that im stuck by the v force stuffer size

I thought you plug was white? Now you're taking about it being wet? You never did say what size that hole was.

[tippmann]

Watch my post scroll down i posted v force plan and the size is wrote there
http://www.3wheelerworld.com/showthr...-My-project-Z-)

Think i have to grind the hole ?

[tippmann]

Ok just put bCk old reed cage and when i snap big gaz throttle he spit prestone So this is my head gasket right ? Or my prestone cap ?

[Mosh]

You mean prestone as Antifreeze/coolant?

Where is that "spitting" from?