Time to ask the experts.

VMAX  Forum

Help Support VMAX Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

capymotiv

Well-Known Member
Joined
Aug 26, 2017
Messages
48
Reaction score
1
Location
Saint Augustine, Fl
Her is the situation. Bought used 88. Popped, sputtered and sometimes stalled at low rpm's but pulled like a horse after 2k rpm. Did the "shotgun" method. Engine seemed to loose throttle response and was just blah afterwards. Not quite a miss but almost as though a dead cylinder. Pulled carbs. Rebuilt all new parts, jets, gaskets, air valves, boots, replaced 1 complete slide (damaged), new diaphragms on others, etc. Reinstall carbs and sync. (They were way out). New battery, good spark at the plugs (have not tested the coils), compression good,Starts right up and idles great now. Bike still feels like a dog with no throttle response. Could I have done something in the air box area to cause this. I hope someone can help me as I have run out of ideas.
 
Did you pull and clean the pilot jet from the jet block? The passage way is very small and easy to clog. You said it seems like a dead cylinder? With it running, I would get a water bottle and spray each pipe coming off of the motor to see if it is "sizzling". If you have one that is cold, then at least you can narrow down the cylinder with the issue.
 
Used a digital thermometer to check temps on pipes and they were even across the pipes +/- 10 degrees. Triple checked for leaks on new boots. V- boost is functioning correctly but still does not feel like it did when I first bought. PO had everything set very rich by the looks of the plugs. Have new intake o-rings on way just in case. I am out of ideas.
 
Is the vboost hooked up and functioning properly ?

Another thing to check.


With the switch in the run position, turn the key on and you will hear the vboost cycle on and off. There will be a clicking from the fuel pump to the rear of the faux tank cover, but the vboost will will make a 'robotic' type noise toward the front of the bike when it cycles on and off.

If the bike is still running rough then I wouldn't suspect a vboost issue, but if it is running smooth and firing on all cylinders, but just doesn't seem to pull up top like it should then it could be an issue.
 
Used a digital thermometer to check temps on pipes and they were even across the pipes +/- 10 degrees. Triple checked for leaks on new boots. V- boost is functioning correctly but still does not feel like it did when I first bought. PO had everything set very rich by the looks of the plugs. Have new intake o-rings on way just in case. I am out of ideas.



Are you POSITIVE that you put the jet block caps back in the proper location all all 4 jet bodies? There are 3 places that the caps will fit, but only 2 actually have jets underneath. One is just a blank hole. I have seen this happen on multiple sets of carbs that have been sent to me. Someone will clean or have the carbs cleaned and then put a jet cap in the wrong place on one of the blocks. Those caps will swell a little bit with time so it might feel too tight in the right place and just right in the wrong place, so people just leave it there.

You say it is rich,

are you float levels set properly? What size main jets are you running?
 
It’s easy to get the two circled ones mixed up. Only the left and middle one should have the caps
 

Attachments

  • 4FF5E1B9-2A6B-4C38-98DE-5812D1E5CD57.jpeg
    4FF5E1B9-2A6B-4C38-98DE-5812D1E5CD57.jpeg
    9.9 KB · Views: 37
Last edited:
That pic messed me up. You may want to circle the two that ARE supposed to be capped rather than circling two holes, only one of which should be capped...
 
Yeah, I'm just trying to help out anyone who may read it quickly and start second guessing how they installed the plugs. In other words, I read your text and saw the photo and interpreted it as the two circled areas need a plug. Maybe others will interpret the same way...but if you're not worried about it, you do you
 
The easiest way, for me, is to look in the holes. The tunnel that is closed off with a brass plug does not need a rubber plug. Small rubber plug goes on left side and bigger plug in the middle.


Sent from my iPhone using Tapatalk
 
Well, turns out that I am an idiot. After pulling the carbs again, found out I was not making sure that the choke was turned all the way off after starting. Turns out there is a slight catch just before it is off that I have been leaving it on. A little sand blasting and vibe polisher made everything all smooth again and spring returns it nicely now, You live and learn.
 

Latest posts

Back
Top